Chimeric antigen receptor and methods of use thereof

ABSTRACT

The present disclosure provides a heterodimeric, conditionally active chimeric antigen receptor (CAR), and a nucleic acid comprising a nucleotide sequence encoding the CAR. The present disclosure provides cells genetically modified to produce the CAR. A CAR of the present disclosure can be used in various methods, which are also provided.

CROSS-REFERENCE

This application claims the benefit of U.S. Provisional Patent Application No. 61/765,585, filed February 15, 2013, which application is incorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

This invention was made with government support under Grant Nos. EY016546 and GM101782 awarded by the National Institutes of Health. The government has certain rights in the invention.

INCORPORATION BY REFERENCE OF SEQUENCE LISTING PROVIDED AS A TEXT FILE

A Sequence Listing is provided herewith as a text file, “UCSF-464WO SeqList_ST25.txt” created on Feb. 13, 2014 and having a size of 153 KB. The contents of the text file are incorporated by reference herein in their entirety.

INTRODUCTION

In cell-based adoptive immunotherapy, immune cells isolated from a patient can be modified to express synthetic proteins that enable the cells to perform new therapeutic functions after they are subsequently transferred back into the patient. An example of such a synthetic protein is a chimeric antigen receptor (CAR). An example of a currently used CAR is a fusion of an extracellular recognition domain (e.g., an antigen-binding domain), a transmembrane domain, and one or more intracellular signaling domains. Upon antigen engagement, the intracellular signaling portion of the CAR can initiate an activation-related response in an immune cell, such are release of cytolytic molecules to induce tumor cell death, etc. However, such CARs are not capable of being pharmacologically controlled. There is a need in the art for a conditionally activatable CAR that can be controlled pharmacologically.

SUMMARY

The present disclosure provides a heterodimeric, conditionally active chimeric antigen receptor (CAR), and a nucleic acid comprising a nucleotide sequence encoding the CAR. The present disclosure provides cells genetically modified to produce the CAR. A CAR of the present disclosure can be used in various methods, which are also provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B provide nucleotide and amino acid sequences of the domains of construct #122.

FIGS. 2A and 2B provide nucleotide and amino acid sequences of the domains of construct #123.

FIGS. 3A and 3B provide nucleotide and amino acid sequences of the domains of construct #125.

FIG. 4 provides nucleotide and amino acid sequences of the domains of construct #126.

FIGS. 5A and 5B provide nucleotide and amino acid sequences of the domains of construct #168.

FIGS. 6A-C provide nucleotide and amino acid sequences of the domains of construct #169.

FIGS. 7A and 7B provide nucleotide and amino acid sequences of the domains of construct #170.

FIGS. 8A and 8B provide nucleotide and amino acid sequences of the domains of construct #197.

FIGS. 9A-C provide nucleotide and amino acid sequences of the domains of construct #206.

FIGS. 10A and 10B provide nucleotide and amino acid sequences of the domains of construct #207.

FIGS. 11A-C provide nucleotide and amino acid sequences of the domains of construct #199.

FIG. 12 depicts IL-2 production triggered by five On-switch CAR variants.

FIG. 13 depicts IL-2 production by control Jurkat lines.

FIG. 14 depicts a comparison between CAR constructs “122+206” and “197+206”.

FIG. 15 depicts cytotoxicity data with the On-switch CAR “197+206.”

FIG. 16 depicts T cell activation data using CAR constructs “122+199”; “197+199”; and “122+168.”

FIG. 17 is a schematic representation of an exemplary On-switch CAR.

FIGS. 18A and 18B depict various exemplary On-switch CAR.

FIGS. 19A-G depict IL-2 production triggered by 3 different On-switch CAR variants recognizing human mesothelin.

FIGS. 20A-C depict IL-2 production triggered by an On-switch CAR variant with a gibberellic acid responsive dimerization pair.

FIGS. 21A-D depict exemplary On-switch CARs and conventional CARs with various co-stimulatory domains.

FIGS. 22A and 22B provide nucleotide and amino acid sequences of the domains of construct #270.

FIGS. 23A and 23B provide nucleotide and amino acid sequences of the domains of construct #300.

FIGS. 24A and 24B provide nucleotide and amino acid sequences of the domains of construct #336.

FIGS. 25A and 25B provide nucleotide and amino acid sequences of the domains of construct #337.

FIGS. 26A and 26B provide nucleotide and amino acid sequences of the domains of construct #357.

FIGS. 27A and 27B provide nucleotide and amino acid sequences of the domains of construct #365.

FIGS. 28A and 28B provide nucleotide and amino acid sequences of the domains of construct #366.

FIGS. 29A and 29B provide nucleotide and amino acid sequences of the domains of construct #367.

FIGS. 30A and 30B provide nucleotide and amino acid sequences of the domains of construct #398.

FIGS. 31A and 31B provide nucleotide and amino acid sequences of the domains of construct #399.

FIGS. 32A and 32B provide nucleotide and amino acid sequences of the domains of construct #400.

FIGS. 33A and 33B provide nucleotide and amino acid sequences of the domains of construct #358.

DEFINITIONS

The terms “polynucleotide” and “nucleic acid,” used interchangeably herein, refer to a polymeric form of nucleotides of any length, either ribonucleotides or deoxyribonucleotides. Thus, this term includes, but is not limited to, single-, double-, or multi-stranded DNA or RNA, genomic DNA, cDNA, DNA-RNA hybrids, or a polymer comprising purine and pyrimidine bases or other natural, chemically or biochemically modified, non-natural, or derivatized nucleotide bases.

The terms “antibodies” and “immunoglobulin” include antibodies or immunoglobulins of any isotype, fragments of antibodies which retain specific binding to antigen, including, but not limited to, Fab, Fv, scFv, and Fd fragments, chimeric antibodies, humanized antibodies, single-chain antibodies, and fusion proteins comprising an antigen-binding portion of an antibody and a non-antibody protein.

“Antibody fragments” comprise a portion of an intact antibody, for example, the antigen binding or variable region of the intact antibody. Examples of antibody fragments include Fab, Fab′, F(ab′)₂, and Fv fragments; diabodies; linear antibodies (Zapata et al., Protein Eng. 8(10): 1057-1062 (1995)); single-chain antibody molecules; and multispecific antibodies formed from antibody fragments. Papain digestion of antibodies produces two identical antigen-binding fragments, called “Fab” fragments, each with a single antigen-binding site, and a residual “Fc” fragment, a designation reflecting the ability to crystallize readily. Pepsin treatment yields an F(ab′)₂ fragment that has two antigen combining sites and is still capable of cross-linking antigen.

“Single-chain Fv” or “sFv” antibody fragments comprise the V_(H) and V_(L) domains of antibody, wherein these domains are present in a single polypeptide chain. In some embodiments, the Fv polypeptide further comprises a polypeptide linker between the V_(H) and V_(L) domains, which enables the sFv to form the desired structure for antigen binding. For a review of sFv, see Pluckthun in The Pharmacology of Monoclonal Antibodies, vol. 113, Rosenburg and Moore eds., Springer-Verlag, New York, pp. 269-315 (1994).

As used herein, the term “affinity” refers to the equilibrium constant for the reversible binding of two agents and is expressed as a dissociation constant (Kd). Affinity can be at least 1-fold greater, at least 2-fold greater, at least 3-fold greater, at least 4-fold greater, at least 5-fold greater, at least 6-fold greater, at least 7-fold greater, at least 8-fold greater, at least 9-fold greater, at least 10-fold greater, at least 20-fold greater, at least 30-fold greater, at least 40-fold greater, at least 50-fold greater, at least 60-fold greater, at least 70-fold greater, at least 80-fold greater, at least 90-fold greater, at least 100-fold greater, or at least 1000-fold greater, or more, than the affinity of an antibody for unrelated amino acid sequences. Affinity of an antibody to a target protein can be, for example, from about 100 nanomolar (nM) to about 0.1 nM, from about 100 nM to about 1 picomolar (pM), or from about 100 nM to about 1 femtomolar (fM) or more. As used herein, the term “avidity” refers to the resistance of a complex of two or more agents to dissociation after dilution. The terms “immunoreactive” and “preferentially binds” are used interchangeably herein with respect to antibodies and/or antigen-binding fragments.

The term “binding” refers to a direct association between two molecules, due to, for example, covalent, electrostatic, hydrophobic, and ionic and/or hydrogen-bond interactions, including interactions such as salt bridges and water bridges. Non-specific binding would refer to binding with an affinity of less than about 10⁻⁷ M, e.g., binding with an affinity of 10⁻⁶ M, 10⁻⁵ M, 10⁻⁴ M, etc.

As used herein, the term “hinge region” refers to a flexible polypeptide connector region (also referred to herein as “hinge” or “spacer”) providing structural flexibility and spacing to flanking polypeptide regions and can consist of natural or synthetic polypeptides. A “hinge region” derived from an immunoglobulin (e.g., IgG1) is generally defined as stretching from Glu₂₁₆ to Pro₂₃₀ of human IgG1 (Burton (1985) Molec. Immunol., 22:161-206). Hinge regions of other IgG isotypes may be aligned with the IgG1 sequence by placing the first and last cysteine residues forming inter-heavy chain disulfide (S—S) bonds in the same positions. The hinge region may be of natural occurrence or non-natural occurrence, including but not limited to an altered hinge region as described in U.S. Pat. No. 5,677,425. The hinge region can include complete hinge region derived from an antibody of a different class or subclass from that of the CH1 domain. The term “hinge region” can also include regions derived from CD8 and other receptors that provide a similar function in providing flexibility and spacing to flanking regions.

An “isolated” polypeptide is one that has been identified and separated and/or recovered from a component of its natural environment. Contaminant components of its natural environment are materials that would interfere with diagnostic or therapeutic uses for the polypeptide, and may include enzymes, hormones, and other proteinaceous or nonproteinaceous solutes. In some embodiments, the polypeptide will be purified (1) to greater than 90%, greater than 95%, or greater than 98%, by weight of antibody as determined by the Lowry method, for example, more than 99% by weight, (2) to a degree sufficient to obtain at least 15 residues of N-terminal or internal amino acid sequence by use of a spinning cup sequenator, or (3) to homogeneity by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) under reducing or nonreducing conditions using Coomassie blue or silver stain. Isolated polypeptide includes the polypeptide in situ within recombinant cells since at least one component of the polypeptide's natural environment will not be present. In some instances, isolated polypeptide will be prepared by at least one purification step.

As used herein, the term “immune cells” generally includes white blood cells (leukocytes) which are derived from hematopoietic stem cells (HSC) produced in the bone marrow. “Immune cells” includes, e.g., lymphocytes (T cells, B cells, natural killer (NK) cells) and myeloid-derived cells (neutrophil, eosinophil, basophil, monocyte, macrophage, dendritic cells).

“T cell” includes all types of immune cells expressing CD3 including T-helper cells (CD4⁺ cells), cytotoxic T-cells (CD8⁺ cells), T-regulatory cells (Treg) and gamma-delta T cells.

A “cytotoxic cell” includes CD8⁺ T cells, natural-killer (NK) cells, and neutrophils, which cells are capable of mediating cytotoxicity responses.

As used herein, the term “stem cell” generally includes pluripotent or multipotent stem cells. “Stem cells” includes, e.g., embryonic stem cells (ES); mesenchymal stem cells (MSC); induced-pluripotent stem cells (iPS); and committed progenitor cells (hematopoeitic stem cells (HSC); bone marrow derived cells, etc.).

As used herein, the terms “treatment,” “treating,” and the like, refer to obtaining a desired pharmacologic and/or physiologic effect. The effect may be prophylactic in terms of completely or partially preventing a disease or symptom thereof and/or may be therapeutic in terms of a partial or complete cure for a disease and/or adverse effect attributable to the disease. “Treatment,” as used herein, covers any treatment of a disease in a mammal, e.g., in a human, and includes: (a) preventing the disease from occurring in a subject which may be predisposed to the disease but has not yet been diagnosed as having it; (b) inhibiting the disease, i.e., arresting its development; and (c) relieving the disease, i.e., causing regression of the disease.

The terms “individual,” “subject,” “host,” and “patient,” used interchangeably herein, refer to a mammal, including, but not limited to, murines (e.g., rats, mice), lagomorphs (e.g., rabbits), non-human primates, humans, canines, felines, ungulates (e.g., equines, bovines, ovines, porcines, caprines), etc.

A “therapeutically effective amount” or “efficacious amount” refers to the amount of an agent, or combined amounts of two agents, that, when administered to a mammal or other subject for treating a disease, is sufficient to effect such treatment for the disease. The “therapeutically effective amount” will vary depending on the agent(s), the disease and its severity and the age, weight, etc., of the subject to be treated.

Before the present invention is further described, it is to be understood that this invention is not limited to particular embodiments described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims.

Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges, and are also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention, the preferred methods and materials are now described. All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited.

It must be noted that as used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a chimeric antigen receptor” includes a plurality of such chimeric antigen receptor and reference to “the dimerizer-binding pair” includes reference to one or more dimerizer-binding pairs and equivalents thereof known to those skilled in the art, and so forth. It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for use of such exclusive terminology as “solely,” “only” and the like in connection with the recitation of claim elements, or use of a “negative” limitation.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. All combinations of the embodiments pertaining to the invention are specifically embraced by the present invention and are disclosed herein just as if each and every combination was individually and explicitly disclosed. In addition, all sub-combinations of the various embodiments and elements thereof are also specifically embraced by the present invention and are disclosed herein just as if each and every such sub-combination was individually and explicitly disclosed herein.

The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present invention is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed.

DETAILED DESCRIPTION

The present disclosure provides a heterodimeric, conditionally active chimeric antigen receptor (CAR), and a nucleic acid comprising a nucleotide sequence encoding the CAR. The present disclosure provides cells genetically modified to produce the CAR. A CAR of the present disclosure can be used in various methods, which are also provided.

Heterodimeric, Conditionally Active Chimeric Antigen Receptor.

The present disclosure provides a heterodimeric, conditionally active chimeric antigen receptor, which, for simplicity, is referred to herein as “CAR.”

In some embodiments, a CAR of the present disclosure comprises: a) a first polypeptide comprising: i) a member of a specific binding pair (e.g., an antigen-binding domain); ii) a first modulatory domain; iii) a first member of a dimerization pair; and iv) a transmembrane domain interposed between the member of a specific binding pair (e.g., an antigen-binding domain) and the first modulatory domain; and b) a second polypeptide comprising: i) a transmembrane domain; ii) a second modulatory domain; iii) a second member of the dimerization pair; and iv) an intracellular signaling domain. The modulatory domain can be a co-stimulatory domain.

In some embodiments, a CAR of the present disclosure comprises: a) a first polypeptide comprising: i) a member of a specific binding pair (e.g., an antigen-binding domain); ii) a first co-stimulatory domain; iii) a first member of a dimerization pair (e.g., a dimerizer-binding pair); and iv) a transmembrane domain interposed between the member of a specific binding pair (e.g., an antigen-binding domain) and the first co-stimulatory domain; and b) a second polypeptide comprising: i) a transmembrane domain; ii) a second co-stimulatory domain; iii) a second member of the dimerization pair (e.g., the dimerizer-binding pair); and iv) an intracellular signaling domain.

In some embodiments, a CAR of the present disclosure comprises: a) a first polypeptide comprising: i) a member of a specific binding pair (e.g., an antigen-binding domain); ii) a modulatory domain; iii) a first member of a dimerization pair (e.g., a dimerizer-binding pair); iv) a transmembrane domain interposed between the member of a specific binding pair (e.g., an antigen-binding domain) and the modulatory domain; and b) a second polypeptide comprising: i) a second member of the dimerization pair (e.g., the dimerizer-binding pair); and ii) an intracellular signaling domain. The modulatory domain can be a co-stimulatory domain.

In some embodiments, a CAR of the present disclosure comprises: a) a first polypeptide comprising: i) a member of a specific binding pair (e.g., an antigen-binding domain); ii) a co-stimulatory domain; iii) a first member of a dimerization pair (e.g., a dimerizer-binding pair); iv) a transmembrane domain interposed between the member of a specific binding pair (e.g., an antigen-binding domain) and the co-stimulatory domain; and b) a second polypeptide comprising: i) a second member of the dimerization pair (e.g., the dimerizer-binding pair); and ii) an intracellular signaling domain.

An example of a subject CAR is represented schematically in FIG. 17. A CAR of the present disclosure can be present in the plasma membrane of a eukaryotic cell, e.g., a mammalian cell, where suitable mammalian cells include, but are not limited to, a cytotoxic cell, a T lymphocyte, a stem cell, a progeny of a stem cell, a progenitor cell, a progeny of a progenitor cell, and an NK cell. When present in the plasma membrane of a eukaryotic cell, a CAR of the present disclosure is active in the presence of: 1) a dimerizing agent binds to the first and second members of the dimerizer-binding pair in the CAR, or otherwise induces dimerization of the first and second members of the dimer; and 2) a factor that binds the member of a specific binding pair (e.g., an antigen-binding domain), e.g., an antigen that binds the antigen-binding domain of the CAR. The factor that binds the member of the specific binding pair is a second member of the specific binding pair. The second member of the specific binding pair can be a soluble (e.g., not bound to a cell) factor; a factor present on the surface of a cell such as a target cell; a factor presented on a solid surface; a factor present in a lipid bilayer; and the like. Where the member of a specific binding pair is an antibody, and the second member of the specific binding pair is an antigen, the antigen can be a soluble (e.g., not bound to a cell) antigen; an antigen present on the surface of a cell such as a target cell; an antigen presented on a solid surface; an antigen present in a lipid bilayer; and the like.

In some instances, a CAR of the present disclosure, when present in the plasma membrane of a eukaryotic cell, and when activated by a second member of a specific binding pair that binds the member of the specific-binding pair of the CAR (e.g., an antigen that binds the antigen-binding domain of the CAR) and a dimerizing agent, increases expression of at least one nucleic acid in the cell. For example, in some cases, a CAR of the present disclosure, when present in the plasma membrane of a eukaryotic cell, and when activated by an antigen that binds the antigen-binding domain of the CAR and a dimerizing agent, increases expression of at least one nucleic acid in the cell by at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 40%, at least about 50%, at least about 75%, at least about 2-fold, at least about 2.5-fold, at least about 5-fold, at least about 10-fold, or more than 10-fold, compared with the level of transcription of the nucleic acid in the absence of the antigen and/or the dimerizing agent.

As an example, the second polypeptide of a CAR of the present disclosure can include an immunoreceptor tyrosine-based activation motif (ITAM)-containing intracellular signaling polypeptide; in such cases, a CAR of the present disclosure, when present in the plasma membrane of a eukaryotic cell, and when activated by an antigen that binds the antigen-binding domain of the CAR and a dimerizing agent, increases nuclear factor of activated T cells (NFAT)-dependent transcription. NFAT-dependent transcription includes transcription induced by any member of the NFAT family, including, e.g., NFATc1, NFATc2, NFATc3, NFATc4, NFAT5; AP-1; Spl; NKκB; and the like.

A CAR of the present disclosure, when present in the plasma membrane of a eukaryotic cell, and when activated by an antigen that binds the antigen-binding domain of the CAR and a dimerizing agent, can, in some instances, result in increased production of one or more cytokines by the cell. For example, a CAR of the present disclosure, when present in the plasma membrane of a eukaryotic cell, and when activated by an antigen that binds the antigen-binding domain of the CAR and a dimerizing agent, can increase production of a cytokine by the cell by at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 40%, at least about 50%, at least about 75%, at least about 2-fold, at least about 2.5-fold, at least about 5-fold, at least about 10-fold, or more than 10-fold, compared with the amount of cytokine produced by the cell in the absence of the antigen and/or the dimerizing agent. Cytokines whose production can be increased include, but are not limited to, an interferon, e.g., IL-2, interferon gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), IL-15, IL-12, IL-4, IL-5, IL-10; a chemokine; a growth factor; and the like.

In some cases, a CAR of the present disclosure, when present in the plasma membrane of a eukaryotic cell, and when activated by an antigen that binds the antigen-binding domain of the CAR and a dimerizing agent, can result in both an increase in transcription of a nucleic acid in the cell and an increase in production of a cytokine by the cell.

In some instances, a CAR of the present disclosure, when present in the plasma membrane of a eukaryotic cell, and when activated by a dimerizing agent, results in cytotoxic activity by the cell toward a target cell that expresses on its cell surface an antigen to which the antigen-binding domain of the first polypeptide of the CAR binds. For example, where the eukaryotic cell is a cytotoxic cell (e.g., an NK cell or a cytotoxic T lymphocyte), a CAR of the present disclosure, when present in the plasma membrane of the cell, and when activated by a dimerizing agent, increases cytotoxic activity of the cell toward a target cell that expresses on its cell surface an antigen to which the antigen-binding domain of the first polypeptide of the CAR binds. For example, where the eukaryotic cell is an NK cell or a T lymphocyte, a CAR of the present disclosure, when present in the plasma membrane of the cell, and when activated by a dimerizing agent, increases cytotoxic activity of the cell by at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 40%, at least about 50%, at least about 75%, at least about 2-fold, at least about 2.5-fold, at least about 5-fold, at least about 10-fold, or more than 10-fold, compared to the cytotoxic activity of the cell in the absence of the dimerizing agent.

In some cases, a CAR of the present disclosure, when present in the plasma membrane of a eukaryotic cell, and when activated by an antigen that binds the antigen-binding domain of the CAR and a dimerizing agent, can result in other CAR activation related events such as proliferation and expansion (either due to increased cellular division or anti-apoptotic responses).

In some cases, a CAR of the present disclosure, when present in the plasma membrane of a eukaryotic cell, and when activated by an antigen that binds the antigen-binding domain of the CAR and a dimerizing agent, can result in other CAR activation related events such as intracellular signaling modulation, cellular differentiation, or cell death.

A CAR of the present disclosure can be present in a eukaryotic cell membrane, where the first and second polypeptides of the CAR are not covalently linked to one another. A CAR of the present disclosure can be present in a eukaryotic cell membrane as a single heterodimer that is not covalently linked to any other polypeptide in the membrane. Alternatively, a first CAR of the present disclosure can be present in a eukaryotic cell membrane as a heterodimer that is covalently or non-covalently linked to a second CAR of the present disclosure. In some cases, the first and the second CAR are covalently linked via a disulfide bond formed between cysteines present in a hinge region present in both the first polypeptide of the first CAR and the first polypeptide of the second CAR.

In some cases, a CAR of the present disclosure can be present in a eukaryotic cell membrane, where the first polypeptides of the CAR comprise an antibody fragment and the second polypeptides of the CAR comprise a signal transducing domain derived from a cytokine receptor, such that, upon dimerization, the CAR may represent a heterodimeric-signalobody CAR, e.g., a signalobody composed of at least two independent polypeptides. A “signalobody”, as it is known in the art, is a single chimeric macromolecule composed of an antibody fragment and a signal transduction domain derived from a cytokine receptor. In certain instances, a heterodimeric-signalobody CAR of the present disclosure, when present in the cell membrane of a eukaryotic cell, dimerized by a dimerizer, and activated by an antigen, e.g., an oligomerized antigen, may induce the oligomerization of the heterodimeric-signalobody CAR. Such ligand-induced oligomerization of a heterodimeric-signalobody CAR may activate, e.g., increase, or perpetuate, e.g., maintain, signal transduction, e.g., ligand-induced oligomerization of a heterodimeric-signalobody CAR may transmit a signal eliciting a cellular response. In some instances, a plurality of heterodimeric-signalobody CARs may be utilized combinatorially to elicit a desired cellular response.

Member of a Specific Binding Pair

A CAR of the present disclosure includes a member of a specific binding pair. Specific binding pairs include, but are not limited to, antigen-antibody binding pairs; ligand-receptor binding pairs; and the like. Thus, a member of a specific binding pair suitable for use in a CAR of the present disclosure includes an antigen; an antibody; a ligand; and a ligand-binding receptor.

Antigen-Binding Domain

An antigen-binding domain suitable for use in a CAR of the present disclosure can be any antigen-binding polypeptide, a wide variety of which are known in the art. In some instances, the antigen-binding domain is a single chain Fv (scFv). Other antibody based recognition domains (cAb VHH (camelid antibody variable domains) and humanized versions, IgNAR VH (shark antibody variable domains) and humanized versions, sdAb VH (single domain antibody variable domains) and “camelized” antibody variable domains are suitable for use. In some instances, T-cell receptor (TCR) based recognition domains such as single chain TCR (scTv, single chain two-domain TCR containing VαVβ) are also suitable for use.

An antigen-binding domain suitable for use in a CAR of the present disclosure can have a variety of antigen-binding specificities. In some cases, the antigen-binding domain is specific for an epitope present in an antigen that is expressed by (synthesized by) a cancer cell, i.e., a cancer cell associated antigen. The cancer cell associated antigen can be an antigen associated with, e.g., a breast cancer cell, a B cell lymphoma, a Hodgkin lymphoma cell, an ovarian cancer cell, a prostate cancer cell, a mesothelioma, a lung cancer cell (e.g., a small cell lung cancer cell), a non-Hodgkin B-cell lymphoma (B-NHL) cell, an ovarian cancer cell, a prostate cancer cell, a mesothelioma cell, a lung cancer cell (e.g., a small cell lung cancer cell), a melanoma cell, a chronic lymphocytic leukemia cell, an acute lymphocytic leukemia cell, a neuroblastoma cell, a glioma, a glioblastoma, a medulloblastoma, a colorectal cancer cell, etc. A cancer cell associated antigen may also be expressed by a non-cancerous cell.

Non-limiting examples of antigens to which an antigen-binding domain of a subject CAR can bind include, e.g., CD19, CD20, CD38, CD30, Her2/neu, ERBB2, CA125, MUC-1, prostate-specific membrane antigen (PSMA), CD44 surface adhesion molecule, mesothelin, carcinoembryonic antigen (CEA), epidermal growth factor receptor (EGFR), EGFRvIII, vascular endothelial growth factor receptor-2 (VEGFR2), high molecular weight-melanoma associated antigen (HMW-MAA), MAGE-A1, IL-13R-a2, GD2, and the like.

Ligand

In some cases, a member of a specific binding pair suitable for use in a subject CAR is a ligand for a receptor. Ligands include, but are not limited to, cytokines (e.g., IL-13, etc.); growth factors (e.g., heregulin; vascular endothelial growth factor (VEGF); and the like); an integrin-binding peptide (e.g., a peptide comprising the sequence Arg-Gly-Asp); and the like.

Where the member of a specific binding pair in a subject CAR is a ligand, the CAR can be activated in the presence of both a dimerizer agent and a second member of the specific binding pair, where the second member of the specific binding pair is a receptor for the ligand. For example, where the ligand is VEGF, the second member of the specific binding pair can be a VEGF receptor, including a soluble VEGF receptor. As another example, where the ligand is heregulin, the second member of the specific binding pair can be Her2.

Receptors

As noted above, in some cases, the member of a specific binding pair that is included in a subject CAR is a receptor, e.g., a receptor for a ligand, a co-receptor, etc. The receptor can be a ligand-binding fragment of a receptor. Suitable receptors include, but are not limited to, a growth factor receptor (e.g., a VEGF receptor); a killer cell lectin-like receptor subfamily K, member 1 (NKG2D) polypeptide (receptor for MICA, MICB, and ULB6); a cytokine receptor (e.g., an IL-13 receptor; an IL-2 receptor; etc.); Her2; CD27; a natural cytotoxicity receptor (NCR) (e.g., NKP30 (NCR3/CD337) polypeptide (receptor for HLA-B-associated transcript 3 (BAT3) and B7-H6); etc.); etc.

Hinge Region

In some cases, the first polypeptide of a subject CAR comprises a hinge region (also referred to herein as a “spacer”), where the hinge region is interposed between the antigen-binding domain and the transmembrane domain. In some cases, the hinge region is an immunoglobulin heavy chain hinge region. In some cases, the hinge region is a hinge region polypeptide derived from a receptor (e.g., a CD8-derived hinge region).

The hinge region can have a length of from about 4 amino acids to about 50 amino acids, e.g., from about 4 aa to about 10 aa, from about 10 aa to about 15 aa, from about 15 aa to about 20 aa, from about 20 aa to about 25 aa, from about 25 aa to about 30 aa, from about 30 aa to about 40 aa, or from about 40 aa to about 50 aa.

Suitable spacers can be readily selected and can be of any of a number of suitable lengths, such as from 1 amino acid (e.g., Gly) to 20 amino acids, from 2 amino acids to 15 amino acids, from 3 amino acids to 12 amino acids, including 4 amino acids to 10 amino acids, 5 amino acids to 9 amino acids, 6 amino acids to 8 amino acids, or 7 amino acids to 8 amino acids, and can be 1, 2, 3, 4, 5, 6, or 7 amino acids.

Exemplary spacers include glycine polymers (G)_(n), glycine-serine polymers (including, for example, (GS)_(n), (GSGGS)_(n) (SEQ ID NO:37) and (GGGS)_(n) (SEQ ID NO:38), where n is an integer of at least one), glycine-alanine polymers, alanine-serine polymers, and other flexible linkers known in the art. Glycine and glycine-serine polymers can be used; both Gly and Ser are relatively unstructured, and therefore can serve as a neutral tether between components. Glycine polymers can be used; glycine accesses significantly more phi-psi space than even alanine, and is much less restricted than residues with longer side chains (see Scheraga, Rev. Computational Chem. 11173-142 (1992)). Exemplary spacers can comprise amino acid sequences including, but not limited to, GGSG (SEQ ID NO:39), GGSGG (SEQ ID NO:40), GSGSG (SEQ ID NO:41), GSGGG (SEQ ID NO:42), GGGSG (SEQ ID NO:43), GSSSG (SEQ ID NO:44), and the like.

In some cases, the hinge region in the first polypeptide of a subject CAR includes at least one cysteine. For example, in some cases, the hinge region can include the sequence Cys-Pro-Pro-Cys. If present, a cysteine in the hinge region of a first CAR can be available to form a disulfide bond with a hinge region in a second CAR.

Immunoglobulin hinge region amino acid sequences are known in the art; see, e.g., Tan et al. (1990) Proc. Natl. Acad. Sci. USA 87:162; and Huck et al. (1986) Nucl. Acids Res. 14:1779. As non-limiting examples, an immunoglobulin hinge region can include one of the following amino acid sequences: DKTHT (SEQ ID NO:45); CPPC (SEQ ID NO:46); CPEPKSCDTPPPCPR (SEQ ID NO:47) (see, e.g., Glaser et al. (2005) J. Biol. Chem. 280:41494); ELKTPLGDTTHT (SEQ ID NO:48); KSCDKTHTCP (SEQ ID NO:49); KCCVDCP (SEQ ID NO:50); KYGPPCP (SEQ ID NO:51); EPKSCDKTHTCPPCP (SEQ ID NO:52) (human IgG1 hinge); ERKCCVECPPCP (SEQ ID NO:53) (human IgG2 hinge); ELKTPLGDTTHTCPRCP (SEQ ID NO:54) (human IgG3 hinge); SPNMVPHAHHAQ (SEQ ID NO:55) (human IgG4 hinge); and the like.

The hinge region can comprise an amino acid sequence of a human IgG1, IgG2, IgG3, or IgG4, hinge region. The hinge region can include one or more amino acid substitutions and/or insertions and/or deletions compared to a wild-type (naturally-occurring) hinge region. For example, His₂₂₉ of human IgG1 hinge can be substituted with Tyr, so that the hinge region comprises the sequence EPKSCDKTYTCPPCP (SEQ ID NO:52); see, e.g., Yan et al. (2012) J. Biol. Chem. 287:5891.

The hinge region can comprise an amino acid sequence derived from human CD8; e.g., the hinge region can comprise the amino acid sequence: TTTPAPRPPTPAPTIASQPLSLRPEACRPAAGGAVHTRGLDFACD (SEQ ID NO:56), or a variant thereof.

Transmembrane Domain

The first and the second polypeptides of a CAR of the present disclosure include transmembrane domains for insertion into a eukaryotic cell membrane. The transmembrane domain of the first polypeptide is interposed between the antigen-binding domain and the co-stimulatory domain. Where the first polypeptide includes a hinge region, the transmembrane domain is interposed between the hinge region and the co-stimulatory domain, such that the first polypeptide comprises, in order from the amino terminus (N-terminus) to the carboxyl terminus (C-terminus): an antigen-binding domain; a hinge region; a transmembrane domain; a first co-stimulatory domain; and a first member of a dimerizer-binding pair.

The transmembrane domain of the second polypeptide is at or near the N-terminus of the polypeptide, such that the second polypeptide comprises, in order from N-terminus to C-terminus: a transmembrane domain; a second co-stimulatory domain; a second member of the dimerizer-binding pair; and an intracellular signaling domain.

Any transmembrane (TM) domain that provides for insertion of a polypeptide into the cell membrane of a eukaryotic (e.g., mammalian) cell is suitable for use. As one non-limiting example, the TM sequence IYIWAPLAGTCGVLLLSLVITLYC (SEQ ID NO:30) can be used. Additional non-limiting examples of suitable TM sequences include: a) CD8 beta derived: LGLLVAGVLVLLVSLGVAIHLCC (SEQ ID NO:57); b) CD4 derived: ALIVLGGVAGLLLFIGLGIFFCVRC (SEQ ID NO:58); c) CD3 zeta derived: LCYLLDGILFIYGVILTALFLRV (SEQ ID NO:59); d) CD28 derived: WVLVVVGGVLACYSLLVTVAFIIFWV (SEQ ID NO:60); e) CD134 (OX40) derived: VAAILGLGLVLGLLGPLAILLALYLL (SEQ ID NO:61); and f) CD7 derived: ALPAALAVISFLLGLGLGVACVLA (SEQ ID NO:62).

Linkers

In some cases, a first polypeptide of a subject CAR includes a linker between any two adjacent domains. For example, a linker can be disposed between the transmembrane domain and the first co-stimulatory domain of the first polypeptide. As another example, a linker can be disposed between the first co-stimulatory domain and the first member of a dimerizer-binding pair of the first polypeptide. As another example, a linker can be disposed between the transmembrane domain and the second co-stimulatory domain of the second polypeptide. As another example, a linker can be disposed between the second co-stimulatory domain and the second member of the dimerizer-binding pair of the second polypeptide. As another example, a linker can be disposed between the second member of the dimerizer-binding pair and the intracellular signaling domain of the second polypeptide.

The linker peptide may have any of a variety of amino acid sequences. Proteins can be joined by a spacer peptide, generally of a flexible nature, although other chemical linkages are not excluded. A linker can be a peptide of between about 6 and about 40 amino acids in length, or between about 6 and about 25 amino acids in length. These linkers can be produced by using synthetic, linker-encoding oligonucleotides to couple the proteins. Peptide linkers with a degree of flexibility can be used. The linking peptides may have virtually any amino acid sequence, bearing in mind that suitable linkers will have a sequence that results in a generally flexible peptide. The use of small amino acids, such as glycine and alanine, are of use in creating a flexible peptide. The creation of such sequences is routine to those of skill in the art.

Suitable linkers can be readily selected and can be of any of a suitable of different lengths, such as from 1 amino acid (e.g., Gly) to 20 amino acids, from 2 amino acids to 15 amino acids, from 3 amino acids to 12 amino acids, including 4 amino acids to 10 amino acids, 5 amino acids to 9 amino acids, 6 amino acids to 8 amino acids, or 7 amino acids to 8 amino acids, and may be 1, 2, 3, 4, 5, 6, or 7 amino acids.

Exemplary flexible linkers include glycine polymers (G)_(n), glycine-serine polymers (including, for example, (GS)_(n), GSGGS_(n) (SEQ ID NO:37) and GGGS_(n) (SEQ ID NO:38), where n is an integer of at least one), glycine-alanine polymers, alanine-serine polymers, and other flexible linkers known in the art. Glycine and glycine-serine polymers are of interest since both of these amino acids are relatively unstructured, and therefore may serve as a neutral tether between components. Glycine polymers are of particular interest since glycine accesses significantly more phi-psi space than even alanine, and is much less restricted than residues with longer side chains (see Scheraga, Rev. Computational Chem. 11173-142 (1992)). Exemplary flexible linkers include, but are not limited GGSG (SEQ ID NO:39), GGSGG (SEQ ID NO:40), GSGSG (SEQ ID NO:41), GSGGG (SEQ ID NO:42), GGGSG (SEQ ID NO:43), GSSSG (SEQ ID NO:44), and the like. The ordinarily skilled artisan will recognize that design of a peptide conjugated to any elements described above can include linkers that are all or partially flexible, such that the linker can include a flexible linker as well as one or more portions that confer less flexible structure.

Modulatory Domains

Modulatory domains suitable for use in a CAR of the present disclosure include co-stimulatory domains.

In some cases, the modulatory domain on the first polypeptide of a subject CAR has substantially the same amino acid sequence as the modulatory domain on the second polypeptide of the CAR. For example, in some cases, the modulatory domain on the first polypeptide of a CAR comprises an amino acid sequence that is at least about 90%, at least about 95%, at least about 98%, at least about 99%, or 100%, identical to the amino acid sequence of the modulatory domain on the second polypeptide of the CAR. The modulatory domain of the first polypeptide of a subject CAR can have substantially the same length as the modulatory domain of the second polypeptide of a subject CAR; e.g., the first and second modulatory domains can differ in length from one another by fewer than 10 amino acids, or fewer than 5 amino acids. In some cases, the first and second modulatory domains have the same length.

A modulatory domain suitable for inclusion in the first and the second polypeptide of a subject CAR can have a length of from about 30 amino acids to about 70 amino acids (aa), e.g., a modulatory domain can have a length of from about 30 aa to about 35 aa, from about 35 aa to about 40 aa, from about 40 aa to about 45 aa, from about 45 aa to about 50 aa, from about 50 aa to about 55 aa, from about 55 aa to about 60 aa, from about 60 aa to about 65 aa, or from about 65 aa to about 70 aa. In other cases, modulatory domain can have a length of from about 70 aa to about 100 aa, from about 100 aa to about 200 aa, or greater than 200 aa.

Co-stimulatory domains suitable for use in a CAR of the present disclosure are generally polypeptides derived from receptors. In some embodiments, co-stimulatory domains homodimerize. A subject co-stimulatory domain can be an intracellular portion of a transmembrane protein (i.e., the co-stimulatory domain can be derived from a transmembrane protein). Non-limiting examples of suitable co-stimulatory polypeptides include, but are not limited to, 4-1BB (CD137), CD28, ICOS, OX-40, BTLA, CD27, CD30, GITR, and HVEM.

In some cases, the co-stimulatory domain on the first polypeptide of a subject CAR has substantially the same amino acid sequence as the co-stimulatory domain on the second polypeptide of the CAR. For example, in some cases, the co-stimulatory domain on the first polypeptide of a CAR comprises an amino acid sequence that is at least about 90%, at least about 95%, at least about 98%, at least about 99%, or 100%, identical to the amino acid sequence of the co-stimulatory domain on the second polypeptide of the CAR. The co-stimulatory domain of the first polypeptide of a subject CAR can have substantially the same length as the co-stimulatory domain of the second polypeptide of a subject CAR; e.g., the first and second co-stimulatory domains can differ in length from one another by fewer than 10 amino acids, or fewer than 5 amino acids. In some cases, the first and second co-stimulatory domains have the same length.

A co-stimulatory domain suitable for inclusion in the first and the second polypeptide of a subject CAR can have a length of from about 30 amino acids to about 70 amino acids (aa), e.g., a co-stimulatory domain can have a length of from about 30 aa to about 35 aa, from about 35 aa to about 40 aa, from about 40 aa to about 45 aa, from about 45 aa to about 50 aa, from about 50 aa to about 55 aa, from about 55 aa to about 60 aa, from about 60 aa to about 65 aa, or from about 65 aa to about 70 aa. In other cases, the co-stimulatory domain can have a length of from about 70 aa to about 100 aa, from about 100 aa to about 200 aa, or greater than 200 aa.

In some cases, the co-stimulatory domain is derived from an intracellular portion of the transmembrane protein 4-1BB (also known as TNFRSF9; CD137; 4-1BB; CDw137; ILA; etc.). For example, a suitable co-stimulatory domain can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100% amino acid sequence identity to the following amino acid sequence:

KRGRKKLLYIFKQPFMRPVQTTQEEDGCSCRFPEEEEGGCEL (SEQ ID NO:24). In some of these embodiments, the co-stimulatory domain of both the first and the second polypeptide has a length of from about 30 aa to about 35 aa, from about 35 aa to about 40 aa, from about 40 aa to about 45 aa, from about 45 aa to about 50 aa, from about 50 aa to about 55 aa, from about 55 aa to about 60 aa, from about 60 aa to about 65 aa, or from about 65 aa to about 70 aa.

In some cases, the co-stimulatory domain is derived from an intracellular portion of the transmembrane protein CD28 (also known as Tp44). For example, a suitable co-stimulatory domain can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100% amino acid sequence identity to the following amino acid sequence:

(SEQ ID NO: 63) FWVRSKRSRLLHSDYMNMTPRRPGPTRKHYQPYAPPRDFAAYRS. In some of these embodiments, the co-stimulatory domain of both the first and the second polypeptide has a length of from about 30 aa to about 35 aa, from about 35 aa to about 40 aa, from about 40 aa to about 45 aa, from about 45 aa to about 50 aa, from about 50 aa to about 55 aa, from about 55 aa to about 60 aa, from about 60 aa to about 65 aa, or from about 65 aa to about 70 aa.

In some cases, the co-stimulatory domain is derived from an intracellular portion of the transmembrane protein ICOS (also known as AILIM, CD278, and CVID1). For example, a suitable co-stimulatory domain can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100% amino acid sequence identity to the following amino acid sequence:

TKKKYSSSVHDPNGEYMFMRAVNTAKKSRLTDVTL (SEQ ID NO:64). In some of these embodiments, the co-stimulatory domain of both the first and the second polypeptide has a length of from about 30 aa to about 35 aa, from about 35 aa to about 40 aa, from about 40 aa to about 45 aa, from about 45 aa to about 50 aa, from about 50 aa to about 55 aa, from about 55 aa to about 60 aa, from about 60 aa to about 65 aa, or from about 65 aa to about 70 aa.

In some cases, the co-stimulatory domain is derived from an intracellular portion of the transmembrane protein OX-40 (also known as TNFRSF4, RP5-902P8.3, ACT35, CD134, OX40, TXGP1L). For example, a suitable co-stimulatory domain can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100% amino acid sequence identity to the following amino acid sequence:

RRDQRLPPDAHKPPGGGSFRTPIQEEQADAHSTLAKI (SEQ ID NO:65). In some of these embodiments, the co-stimulatory domain of both the first and the second polypeptide has a length of from about 30 aa to about 35 aa, from about 35 aa to about 40 aa, from about 40 aa to about 45 aa, from about 45 aa to about 50 aa, from about 50 aa to about 55 aa, from about 55 aa to about 60 aa, from about 60 aa to about 65 aa, or from about 65 aa to about 70 aa.

In some cases, the co-stimulatory domain is derived from an intracellular portion of the transmembrane protein BTLA (also known as BTLA1 and CD272). For example, a suitable co-stimulatory domain can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100% amino acid sequence identity to the following amino acid sequence:

(SEQ ID NO: 66) CCLRRHQGKQNELSDTAGREINLVDAHLKSEQTEASTRQNSQVLLSETGI YDNDPDLCFRMQEGSEVYSNPCLEENKPGIVYASLNHSVIGPNSRLARNV KEAPTEYASICVRS.

In some cases, the co-stimulatory domain is derived from an intracellular portion of the transmembrane protein CD27 (also known as S152, T14, TNFRSF7, and Tp55). For example, a suitable co-stimulatory domain can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100% amino acid sequence identity to the following amino acid sequence:

HQRRKYRSNKGESPVEPAEPCRYSCPREEEGSTIPIQEDYRKPEPACSP (SEQ ID NO:67). In some of these embodiments, the co-stimulatory domain of both the first and the second polypeptide has a length of from about 30 aa to about 35 aa, from about 35 aa to about 40 aa, from about 40 aa to about 45 aa, from about 45 aa to about 50 aa, from about 50 aa to about 55 aa, from about 55 aa to about 60 aa, from about 60 aa to about 65 aa, or from about 65 aa to about 70 aa.

In some cases, the co-stimulatory domain is derived from an intracellular portion of the transmembrane protein CD30 (also known as TNFRSF8, D1S166E, and Ki-1). For example, a suitable co-stimulatory domain can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100% amino acid sequence identity to a contiguous stretch of from about 100 amino acids to about 110 amino acids (aa), from about 110 aa to about 115 aa, from about 115 aa to about 120 aa, from about 120 aa to about 130 aa, from about 130 aa to about 140 aa, from about 140 aa to about 150 aa, from about 150 aa to about 160 aa, or from about 160 aa to about 185 aa of the following amino acid sequence:

(SEQ ID NO: 68) RRACRKRIRQKLHLCYPVQTSQPKLELVDSRPRRSSTQLRSGASVTEPVA EERGLMSQPLMETCHSVGAAYLESLPLQDASPAGGPSSPRDLPEPRVSTE HTNNKIEKIYIMKADTVIVGTVKAELPEGRGLAGPAEPELEEELEADHTP HYPEQETEPPLGSCSDVMLSVEEEGKEDPLPTAASGK.

In some cases, the co-stimulatory domain is derived from an intracellular portion of the transmembrane protein GITR (also known as TNFRSF18, RP5-902P8.2, AITR, CD357, and GITR-D). For example, a suitable co-stimulatory domain can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100% amino acid sequence identity to the following amino acid sequence:

HIVVQLRSQCMWPRETQLLLEVPPSTEDARSCQFPEEERGERSAEEKGRLGDLWV (SEQ ID NO:69). In some of these embodiments, the co-stimulatory domain of both the first and the second polypeptide has a length of from about 30 aa to about 35 aa, from about 35 aa to about 40 aa, from about 40 aa to about 45 aa, from about 45 aa to about 50 aa, from about 50 aa to about 55 aa, from about 55 aa to about 60 aa, from about 60 aa to about 65 aa, or from about 65 aa to about 70 aa.

In some cases, the co-stimulatory domain derived from an intracellular portion of the transmembrane protein HVEM (also known as TNFRSF14, RP3-395M20.6, ATAR, CD270, HVEA, HVEM, LIGHTR, and TR2). For example, a suitable co-stimulatory domain can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100% amino acid sequence identity to the following amino acid sequence:

CVKRRKPRGDVVKVIVSVQRKRQEAEGEATVIEALQAPPDVTTVAVEETIPSFTGRS PNH (SEQ ID NO:70). In some of these embodiments, the co-stimulatory domain of both the first and the second polypeptide has a length of from about 30 aa to about 35 aa, from about 35 aa to about 40 aa, from about 40 aa to about 45 aa, from about 45 aa to about 50 aa, from about 50 aa to about 55 aa, from about 55 aa to about 60 aa, from about 60 aa to about 65 aa, or from about 65 aa to about 70 aa.

Dimer Pairs

Dimer pairs suitable for use in a subject CAR include dimerizer-binding pairs. Dimerizer-binding pairs suitable for use in a CAR of the present disclosure are in some embodiments polypeptides that bind to a different site of the same molecule (referred to herein as a “dimerizer”). In the presence of a dimerizer, both members of the dimerizer-binding pair bind to a different site of the dimerizer and are thus brought into proximity with one another. In some embodiments, binding to the dimerizer is reversible. In some embodiments, binding to the dimerizer is irreversible. In some embodiments, binding to the dimerizer is non-covalent. In some embodiments, binding to the dimerizer is covalent.

Other dimer pairs suitable for use include dimerizer-binding pairs that dimerize upon binding of a first member of a dimer pair to a dimerizing agent, where the dimerizing agent induces a conformational change in the first member of the dimer pair, and where the conformational change allows the first member of the dimer pair to bind (covalently or non-covalently) to a second member of the dimer pair.

Other dimer pairs suitable for use include dimer pairs in which exposure to light (e.g., blue light) induces dimerization of the dimer pair.

Regardless of the mechanism, the dimer pair will dimerize upon exposure to an agent that induces dimerization, where the agent is in some cases a small molecule, or, in other cases, light. Thus, for simplicity, the discussion below referring to “dimerizer-binding pairs” includes dimer pairs that dimerize regardless of the mechanism.

Non-limiting examples of suitable dimers (e.g., dimerizer-binding pairs) include, but are not limited to:

-   a) FK506 binding protein (FKBP) and FKBP; -   b) FKBP and calcineurin catalytic subunit A (CnA); -   c) FKBP and cyclophilin; -   d) FKBP and FKBP-rapamycin associated protein (FRB); -   e) gyrase B (GyrB) and GyrB; -   f) dihydrofolate reductase (DHFR) and DHFR; -   g) DmrB and DmrB; -   h) PYL and ABI; -   i) Cry2 and CIB1; and -   j) GAI and GID1.

A first or a second member of a dimer (e.g., a dimerizer-binding pair) of a subject CAR can have a length of from about 50 amino acids to about 300 amino acids or more; e.g., a first or a second member of a dimer (e.g., a dimerizer-binding pair) of a subject CAR can have a length of from about 50 aa to about 100 aa, from about 100 aa to about 150 aa, from about 150 aa to about 200 aa, from about 200 aa to about 250 aa, from about 250 aa to about 300 aa, or more than 300 aa.

In some cases, a member of a dimer (e.g., a dimerizer-binding pair) of a subject CAR is derived from FKBP. For example, a suitable dimerizer-binding pair member can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100% amino acid sequence identity to the following amino acid sequence:

(SEQ ID NO: 12) MGVQVETISPGDGRTFPKRGQTCVVHYTGMLEDGKKFDSSRDRNKP FKFMLGKQEVIRGWEEGVAQMSVGQRAKLTISPDYAYGATGHPGII PPHATLVFDVELLKLE.

In some cases, a member of a dimerizer-binding pair of a subject CAR is derived from calcineurin catalytic subunit A (also known as PPP3CA; CALN; CALNA; CALNA1; CCN1; CNA1; PPP2B; CAM-PRP catalytic subunit; calcineurin A alpha; calmodulin-dependent calcineurin A subunit alpha isoform; protein phosphatase 2B, catalytic subunit, alpha isoform; etc.). For example, a suitable dimerizer-binding pair member can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100% amino acid sequence identity to the following amino acid sequence (PP2Ac domain):

(SEQ ID NO: 71) LEESVALRIITEGASILRQEKNLLDIDAPVTVCGDIHGQFFDLMKL FEVGGSPANTRYLFLGDYVDRGYFSIECVLYLWALKILYPKTLFLL RGNHECRHLTEYFTFKQECKIKYSERVYDACMDAFDCLPLAALMNQ QFLCVHGGLSPEINTLDDIRKLDRFKEPPAYGPMCDILWSDPLEDF GNEKTQEHFTHNTVRGCSYFYSYPAVCEFLQHNNLLSILRAHEAQD AGYRMYRKSQTTGFPSLITIFSAPNYLDVYNNKAAVLKYENNVMNI RQFNCSPHPYWLPNFM.

In some cases, a member of a dimer (e.g., a dimerizer-binding pair) is derived from cyclophilin (also known cyclophilin A, PPIA, CYPA, CYPH, PPIase A, etc.). For example, a suitable dimerizer-binding pair member can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100% amino acid sequence identity to the following amino acid sequence:

(SEQ ID NO: 72) MVNPTVFFDIAVDGEPLGRVSFELFADKVPKTAENFRALSTGEKGF GYKGSCFHRIIPGFMCQGGDFTRHNGTGGKSIYGEKFEDENFILKH TGPGILSMANAGPNTNGSQFFICTAKTEWLDGKHVVFGKVKEGMNI VEAMERFGSRNGKTSKKITIADCGQLE.

In some cases, a member of a dimer (e.g., a dimerizer-binding pair) is derived from MTOR (also known as FKBP-rapamycin associated protein; FK506 binding protein 12-rapamycin associated protein 1; FK506 binding protein 12-rapamycin associated protein 2; FK506-binding protein 12-rapamycin complex-associated protein 1; FRAP; FRAP1; FRAP2; RAFT1; and RAPT1). For example, a suitable dimerizer-binding pair member can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100% amino acid sequence identity to the following amino acid sequence (also known as “Frb”: Fkbp-Rapamycin Binding Domain):

(SEQ ID NO: 14) MILWHEMWHEGLEEASRLYFGERNVKGMFEVLEPLHAMMERGPQTL KETSFNQAYGRDLMEAQEWCRKYMKSGNVKDLLQAWDLYYHVFRRI SK.

In some cases, a member of a dimer (e.g., a dimerizer-binding pair) is derived from GyrB (also known as DNA gyrase subunit B). For example, a suitable dimerizer-binding pair member can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100% amino acid sequence identity to a contiguous stretch of from about 100 amino acids to about 200 amino acids (aa), from about 200 aa to about 300 aa, from about 300 aa to about 400 aa, from about 400 aa to about 500 aa, from about 500 aa to about 600 aa, from about 600 aa to about 700 aa, or from about 700 aa to about 800 aa, of the following GyrB amino acid sequence from Escherichia coli (or to the DNA gyrase subunit B sequence from any organism):

MSNSYDSSSIKVLKGLDAVRKRPGMYIGDTDDGTGLHHMVFEVVDNAIDEALAGH CKEIIVTIHADNSVSVQDDGRGIPTGIHPEEGVSAAEVIMTVLHAGGKFDDNSYKVS GGLHGVGVSVVNALSQKLELVIQREGKIHRQIYEHGVPQAPLAVTGETEKTGTMV RFWPSLETFTNVTEFEYEILAKRLRELSFLNSGVSIRLRDKRDGKEDHFHYEGGIKAF VEYLNKNKTPIHPNIFYFSTEKDGIGVEVALQWNDGFQENIYCFTNNIPQRDGGTHL AGFRAAMTRTLNAYMDKEGYSKKAKVSATGDDAREGLIAVVSVKVPDPKFSSQT KDKLVSSEVKSAVEQQMNELLAEYLLENPTDAKIVVGKIIDAARAREAARRAREM TRRKGALDLAGLPGKLADCQERDPALSELYLVEGDSAGGSAKQGRNRKNQAILPL KGKILNVEKARFDKMLSSQEVATLITALGCGIGRDEYNPDKLRYHSIIIMTDADVDG SHIRTLLLTFFYRQMPEIVERGHVYIAQPPLYKVKKGKQEQYIKDDEAMDQYQISIA LDGATLHTNASAPALAGEALEKLVSEYNATQKMINRMERRYPKAMLKELIYQPTL TEADLSDEQTVTRWVNALVSELNDKEQHGSQWKFDVHTNAEQNLFEPIVRVRTHG VDTDYPLDHEFITGGEYRRICTLGEKLRGLLEEDAFIERGERRQPVASFEQALDWLV KESRRGLSIQRYKGLGEMNPEQLWETTMDPESRRMLRVTVKDAIAADQLFTTLMG DAVEPRRAFIEENALKAANIDI (SEQ ID NO:73). In some cases, a member of a dimerizer-binding pair comprises an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100% amino acid sequence identity to amino acids 1-220 of the above-listed GyrB amino acid sequence from Escherichia coli.

In some cases, a member of a dimer (e.g., a dimerizer-binding pair) is derived from DHFR (also known as dihydrofolate reductase, DHFRP1, and DYR). For example, a suitable dimerizer-binding pair member can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100% amino acid sequence identity to the following amino acid sequence:

(SEQ ID NO: 74) MVGSLNCIVAVSQNMGIGKNGDLPWPPLRNEFRYFQRMTTTSSVEG KQNLVIMGKKTWFSIPEKNRPLKGRINLVLSRELKEPPQGAHFLSR SLDDALKLTEQPELANKVDMVWIVGGSSVYKEAMNHPGHLKLFVTR IMQDFESDTFFPEIDLEKYKLLPEYPGVLSDVQEEKGIKYKFEVYE KND.

In some cases, a member of a dimer (e.g., a dimerizer-binding pair) is derived from the DmrB binding domain (i.e., DmrB homodimerization domain). For example, a suitable dimerizer-binding pair member can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100% amino acid sequence identity to the following amino acid sequence:

(SEQ ID NO: 75) MASRGVQVETISPGDGRTFPKRGQTCVVHYTGMLEDGKKVDSSRDR NKPFKFMLGKQEVIRGWEEGVAQMSVGQRAKLTISPDYAYGATGHP GIIPPHATLVFDVELLKLE.

In some cases, a member of a dimer (e.g., a dimerizer-binding pair) is derived from a PYL protein (also known as abscisic acid receptor and as RCAR). For example a member of a subject dimerizer-binding pair can be derived from proteins such as those of Arabidopsis thaliana: PYR1, RCAR1(PYL9), PYL1, PYL2, PYL3, PYL4, PYL5, PYL6, PYL7, PYL8 (RCAR3), PYL10, PYL11, PYL12, PYL13. For example, a suitable dimerizer-binding pair member can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100% amino acid sequence identity to any of the following amino acid sequences:

PYL10: (SEQ ID NO: 76) MNGDETKKVESEYIKKHHRHELVESQCSSTLVKHIKAPLHLVWSIV RRFDEPQKYKPFISRCVVQGKKLEVGSVREVDLKSGLPATKSTEVL EILDDNEHILGIRIVGGDHRLKNYSSTISLHSETIDGKTGTLAIES FVVDVPEGNTKEETCFFVEALIQCNLNSLADVTERLQAESMEKKI. PYL11: (SEQ ID NO: 77) METSQKYHTCGSTLVQTIDAPLSLVWSILRRFDNPQAYKQFVKTCN LSSGDGGEGSVREVTVVSGLPAEFSRERLDELDDESHVMMISIIGG DHRLVNYRSKTMAFVAADTEEKTVVVESYVVDVPEGNSEEETTSFA DTIVGFNLKSLAKLSERVAHLKL PYL12: (SEQ ID NO: 78) MKTSQEQHVCGSTVVQTINAPLPLVWSILRRFDNPKTFKHFVKTCK LRSGDGGEGSVREVTVVSDLPASFSLERLDELDDESHVMVISIIGG DHRLVNYQSKTTVFVAAEEEKTVVVESYVVDVPEGNTEEETTLFAD TIVGCNLRSLAKLSEKMMELT. PYL13: (SEQ ID NO: 79) MESSKQKRCRSSVVETIEAPLPLVWSILRSFDKPQAYQRFVKSCTM RSGGGGGKGGEGKGSVRDVTLVSGFPADFSTERLEELDDESHVMVV SIIGGNHRLVNYKSKTKVVASPEDMAKKTVVVESYVVDVPEGTSEE DTIFFVDNIIRYNLTSLAKLTKKMMK. PYL1: (SEQ ID NO: 80) MANSESSSSPVNEEENSQRISTLHHQTMPSDLTQDEFTQLSQSIAE FHTYQLGNGRCSSLLAQRIHAPPETVWSVVRRFDRPQIYKHFIKSC NVSEDFEMRVGCTRDVNVISGLPANTSRERLDLLDDDRRVTGFSIT GGEHRLRNYKSVTTVHRFEKEEEEERIWTVVLESYVVDVPEGNSEE DTRLFADTVIRLNLQKLASITEAMNRNNNNNNSSQVR. PYL2: (SEQ ID NO: 81) MSSSPAVKGLTDEEQKTLEPVIKTYHQFEPDPTTCTSLITQRIHAP ASVVWPLIRRFDNPERYKHFVKRCRLISGDGDVGSVREVTVISGLP ASTSTERLEFVDDDHRVLSFRVVGGEHRLKNYKSVTSVNEFLNQDS GKVYTVVLESYTVDIPEGNTEEDTKMFVDTVVKLNLQKLGVAATSA PMHDDE. PYL3: (SEQ ID NO: 82) MNLAPIHDPSSSSTTTTSSSTPYGLTKDEFSTLDSIIRTHHTFPRS PNTCTSLIAHRVDAPAHAIVVRFVRDFANPNKYKHFIKSCTIRVNG NGIKEIKVGTIREVSVVSGLPASTSVEILEVLDEEKRILSFRVLGG EHRLNNYRSVTSVNEFVVLEKDKKKRVYSVVLESYIVDIPQGNTEE DTRMFVDTVVKSNLQNLAVISTASPT. PYL4: (SEQ ID NO: 83) MLAVHRPSSAVSDGDSVQIPMMIASFQKRFPSLSRDSTAARFHTHE VGPNQCCSAVIQEISAPISTVWSVVRRFDNPQAYKHFLKSCSVIGG DGDNVGSLRQVHVVSGLPAASSTERLDILDDERHVISFSVVGGDHR LSNYRSVTTLHPSPISGTVVVESYVVDVPPGNTKEETCDFVDVIVR CNLQSLAKIAENTAAESKKKMSL. PYL5: (SEQ ID NO: 84) MRSPVQLQHGSDATNGFHTLQPHDQTDGPIKRVCLTRGMHVPEHVA MHHTHDVGPDQCCSSVVQMIHAPPESVWALVRRFDNPKVYKNFIRQ CRIVQGDGLHVGDLREVMVVSGLPAVSSTERLEILDEERHVISFSV VGGDHRLKNYRSVTTLHASDDEGTVVVESYIVDVPPGNTEEETLSF VDTIVRCNLQSLARSTNRQ. PYL6: (SEQ ID NO: 85) MPTSIQFQRSSTAAEAANATVRNYPHHHQKQVQKVSLTRGMADVPE HVELSHTHVVGPSQCFSVVVQDVEAPVSTVWSILSRFEHPQAYKHF VKSCHVVIGDGREVGSVREVRVVSGLPAAFSLERLEIMDDDRHVIS FSVVGGDHRLMNYKSVTTVHESEEDSDGKKRTRVVESYVVDVPAGN DKEETCSFADTIVRCNLQSLAKLAENTSKFS. PYL7: (SEQ ID NO: 86) MEMIGGDDTDTEMYGALVTAQSLRLRHLHHCRENQCTSVLVKYIQA PVHLVWSLVRRFDQPQKYKPFISRCTVNGDPEIGCLREVNVKSGLP ATTSTERLEQLDDEEHILGINIIGGDHRLKNYSSILTVHPEMIDGR SGTMVMESFVVDVPQGNTKDDTCYFVESLIKCNLKSLACVSERLAA QDITNSIATFCNASNGYREKNHTETNL. PYL8: (SEQ ID NO: 87) MEANGIENLTNPNQEREFIRRHHKHELVDNQCSSTLVKHINAPVHI VWSLVRRFDQPQKYKPFISRCVVKGNMEIGTVREVDVKSGLPATRS TERLELLDDNEHILSIRIVGGDHRLKNYSSIISLHPETIEGRIGTL VIESFVVDVPEGNTKDETCYFVEALIKCNLKSLADISERLAVQDTT ESRV. PYL9: (SEQ ID NO: 88) MMDGVEGGTAMYGGLETVQYVRTHHQHLCRENQCTSALVKHIKAPL HLVWSLVRRFDQPQKYKPFVSRCTVIGDPEIGSLREVNVKSGLPAT TSTERLELLDDEEHILGIKIIGGDHRLKNYSSILTVHPEIIEGRAG TMVIESFVVDVPQGNTKDETCYFVEALIRCNLKSLADVSERLASQD ITQ. PYR1: (SEQ ID NO: 89) MPSELTPEERSELKNSIAEFHTYQLDPGSCSSLHAQRIHAPPELVW SIVRRFDKPQTYKHFIKSCSVEQNFEMRVGCTRDVIVISGLPANTS TERLDILDDERRVTGFSIIGGEHRLTNYKSVTTVHRFEKENRIVVT VVLESYVVDMPEGNSEDDTRMFADTVVKLNLQKLATVAEAMARNSG DGSGSQVT.

In some cases, a member of a dimer (e.g., a dimerizer-binding pair) is derived from an ABI protein (also known as Abscisic Acid-Insensitive). For example a member of a subject dimerizer-binding pair can be derived from proteins such as those of Arabidopsis thaliana: ABI1 (Also known as ABSCISIC ACID-INSENSITIVE 1, Protein phosphatase 2C 56, AtPP2C56, P2C56, and PP2C ABI1) and/or ABI2(also known as P2C77, Protein phosphatase 2C 77, AtPP2C77, ABSCISIC ACID-INSENSITIVE 2, Protein phosphatase 2C ABI2, and PP2C ABI2). For example, a suitable dimerizer-binding pair member can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100% amino acid sequence identity to a contiguous stretch of from about 100 amino acids to about 110 amino acids (aa), from about 110 aa to about 115 aa, from about 115 aa to about 120 aa, from about 120 aa to about 130 aa, from about 130 aa to about 140 aa, from about 140 aa to about 150 aa, from about 150 aa to about 160 aa, from about 160 aa to about 170 aa, from about 170 aa to about 180 aa, from about 180 aa to about 190 aa, or from about 190 aa to about 200 aa of any of the following amino acid sequences:

ABI1: (SEQ ID NO: 90) MEEVSPAIAGPFRPFSETQMDFTGIRLGKGYCNNQYSNQDSENGDL MVSLPETSSCSVSGSHGSESRKVLISRINSPNLNMKESAAADIVVV DISAGDEINGSDITSEKKMISRTESRSLFEFKSVPLYGFTSICGRR PEMEDAVSTIPRFLQSSSGSMLDGRFDPQSAAHFFGVYDGHGGSQV ANYCRERMHLALAEEIAKEKPMLCDGDTWLEKWKKALFNSFLRVDS EIESVAPETVGSTSVVAVVFPSHIFVANCGDSRAVLCRGKTALPLS VDHKPDREDEAARIEAAGGKVIQWNGARVFGVLAMSRSIGDRYLKP SIIPDPEVTAVKRVKEDDCLILASDGVWDVMTDEEACEMARKRILL WHKKNAVAGDASLLADERRKEGKDPAAMSAAEYLSKLAIQRGSKDN ISVVVVDLKPRRKLKSKPLN. ABI2: (SEQ ID NO: 91) MDEVSPAVAVPFRPFTDPHAGLRGYCNGESRVTLPESSCSGDGAMK DSSFEINTRQDSLTSSSSAMAGVDISAGDEINGSDEFDPRSMNQSE KKVLSRTESRSLFEFKCVPLYGVTSICGRRPEMEDSVSTIPRFLQV SSSSLLDGRVTNGFNPHLSAHFFGVYDGHGGSQVANYCRERMHLAL TEEIVKEKPEFCDGDTWQEKWKKALFNSFMRVDSEIETVAHAPETV GSTSVVAVVFPTHIFVANCGDSRAVLCRGKTPLALSVDHKPDRDDE AARIEAAGGKVIRWNGARVFGVLAMSRSIGDRYLKPSVIPDPEVTS VRRVKEDDCLILASDGLWDVMTNEEVCDLARKRILLWHKKNAMAGE ALLPAEKRGEGKDPAAMSAAEYLSKMALQKGSKDNISVVVVDLKGI RKFKSKSLN.

In some cases, a member of a dimer (e.g., a dimerizer-binding pair) is derived from a Cry2 protein (also known as cryptochrome 2). For example a member of a subject dimer (e.g., a dimerizer-binding pair) can be derived from Cry2 proteins from any organism (e.g., a plant) such as, but not limited to, those of Arabidopsis thaliana. For example, a suitable dimerizer-binding pair member can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100% amino acid sequence identity to a contiguous stretch of from about 100 amino acids to about 110 amino acids (aa), from about 110 aa to about 115 aa, from about 115 aa to about 120 aa, from about 120 aa to about 130 aa, from about 130 aa to about 140 aa, from about 140 aa to about 150 aa, from about 150 aa to about 160 aa, from about 160 aa to about 170 aa, from about 170 aa to about 180 aa, from about 180 aa to about 190 aa, or from about 190 aa to about 200 aa of any of the following amino acid sequences:

Cry2 (Arabidopsis thaliana)

(SEQ ID NO: 92) MKMDKKTIVWFRRDLRIEDNPALAAAAHEGSVFPVFIVVCPEEEGQ FYPGRASRWWMKQSLAHLSQSLKALGSDLTLIKTHNTISAILDCIR VTGATKVVFNHLYDPVSLVRDHTVKEKLVERGISVQSYNGDLLYEP WEIYCEKGKPFTSFNSYWKKCLDMSIESVMLPPPWRLMPITAAAEA IWACSIEELGLENEAEKPSNALLTRAWSPGWSNADKLLNEFIEKQL IDYAKNSKKVVGNSTSLLSPYLHFGEISVRHVFQCARMKQIIWARD KNSEGEESADLFLRGIGLREYSRYICFNFPFTHEQSLLSHLRFFPW DADVDKFKAWRQGRTGYPLVDAGMRELWATGWMHNRIRVIVSSFAV KFLLLPWKWGMKYFWDTLLDADLECDILGWQYISGSIPDGHELDRL DNPALQGAKYDPEGEYIRQWLPELARLPTEWIHHPWDAPLTVLKAS GVELGTNYAKPIVDIDTARELLAKAISRTREAQIMIGAAPDEIVAD SFEALGANTIKEPGLCPSVSSNDQQVPSAVRYNGSKRVKPEEEEER DMKKSRGFDERELFSTAESSSSSSVFFVSQSCSLASEGKNLEGIQD SSDQITTSLGKNGCK.

In some cases, a member of a dimer (e.g., a dimerizer-binding pair) is derived from the CIB1 Arabidopsis thaliana protein (also known as transcription factor bHLH63). For example, a suitable dimer (e.g., a dimerizer-binding pair) member can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100% amino acid sequence identity to a contiguous stretch of from about 100 amino acids to about 110 amino acids (aa), from about 110 aa to about 115 aa, from about 115 aa to about 120 aa, from about 120 aa to about 130 aa, from about 130 aa to about 140 aa, from about 140 aa to about 150 aa, from about 150 aa to about 160 aa, from about 160 aa to about 170 aa, from about 170 aa to about 180 aa, from about 180 aa to about 190 aa, or from about 190 aa to about 200 aa of the following amino acid sequence:

(SEQ ID NO: 93) MNGAIGGDLLLNFPDMSVLERQRAHLKYLNPTFDSPLAGFFADSSM ITGGEMDSYLSTAGLNLPMMYGETTVEGDSRLSISPETTLGTGNFK KRKFDTETKDCNEKKKKMTMNRDDLVEEGEEEKSKITEQNNGSTKS IKKMKHKAKKEENNFSNDSSKVTKELEKTDYIHVRARRGQATDSHS IAERVRREKISERMKFLQDLVPGCDKITGKAGMLDEIINYVQSLQR QIEFLSMKLAIVNPRPDFDMDDIFAKEVASTPMTVVPSPEMVLSGY SHEMVHSGYSSEMVNSGYLHVNPMQQVNTSSDPLSCFNNGEAPSMW DSHVQNLYGNLGV.

In some cases, a member of a dimer (e.g., a dimerizer-binding pair) is derived from the GAI Arabidopsis thaliana protein (also known as Gibberellic Acid Insensitive, and DELLA protein GAI). For example, a suitable dimerizer-binding pair member can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100% amino acid sequence identity to a contiguous stretch of from about 100 amino acids to about 110 amino acids (aa), from about 110 aa to about 115 aa, from about 115 aa to about 120 aa, from about 120 aa to about 130 aa, from about 130 aa to about 140 aa, from about 140 aa to about 150 aa, from about 150 aa to about 160 aa, from about 160 aa to about 170 aa, from about 170 aa to about 180 aa, from about 180 aa to about 190 aa, or from about 190 aa to about 200 aa of the following amino acid sequence:

(SEQ ID NO: 94) MKRDHHHHHHQDKKTMMMNEEDDGNGMDELLAVLGYKVRSSEMADV AQKLEQLEVMMSNVQEDDLSQLATETVHYNPAELYTWLDSMLTDLN PPSSNAEYDLKAIPGDAILNQFAIDSASSSNQGGGGDTYTTNKRLK CSNGVVETTTATAESTRHVVLVDSQENGVRLVHALLACAEAVQKEN LTVAEALVKQIGFLAVSQIGAMRKVATYFAEALARRIYRLSPSQSP IDHSLSDTLQMHFYETCPYLKFAHFTANQAILEAFQGKKRVHVIDF SMSQGLQWPALMQALALRPGGPPVFRLTGIGPPAPDNFDYLHEVGC KLAHLAEAIHVEFEYRGFVANTLADLDASMLELRPSEIESVAVNSV FELHKLLGRPGAIDKVLGVVNQIKPEIFTVVEQESNHNSPIFLDRF TESLHYYSTLFDSLEGVPSGQDKVMSEVYLGKQICNVVACDGPDRV ERHETLSQWRNRFGSAGFAAAHIGSNAFKQASMLLALFNGGEGYRV EESDGCLMLGWHTRPLIATSAWKLSTN.

In some cases, a member of a dimer (e.g., a dimerizer-binding pair) is derived from a GID1 Arabidopsis thaliana protein (also known as Gibberellin receptor GID1). For example, a suitable dimer member can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100% amino acid sequence identity to a contiguous stretch of from about 100 amino acids to about 110 amino acids (aa), from about 110 aa to about 115 aa, from about 115 aa to about 120 aa, from about 120 aa to about 130 aa, from about 130 aa to about 140 aa, from about 140 aa to about 150 aa, from about 150 aa to about 160 aa, from about 160 aa to about 170 aa, from about 170 aa to about 180 aa, from about 180 aa to about 190 aa, or from about 190 aa to about 200 aa of any of the following amino acid sequences:

GID1A: (SEQ ID NO: 95) MAASDEVNLIESRTVVPLNTWVLISNFKVAYNILRRPDGTFNRHLA EYLDRKVTANANPVDGVFSFDVLIDRRINLLSRVYRPAYADQEQPP SILDLEKPVDGDIVPVILFFHGGSFAHSSANSAIYDTLCRRLVGLC KCVVVSVNYRRAPENPYPCAYDDGWIALNWVNSRSWLKSKKDSKVH IFLAGDSSGGNIAHNVALRAGESGIDVLGNILLNPMFGGNERTESE KSLDGKYFVTVRDRDWYWKAFLPEGEDREHPACNPFSPRGKSLEGV SFPKSLVVVAGLDLIRDWQLAYAEGLKKAGQEVKLMHLEKATVGFY LLPNNNHFHNVMDEISAFVNAEC. GID1B: (SEQ ID NO: 96) MAGGNEVNLNECKRIVPLNTWVLISNFKLAYKVLRRPDGSFNRDLA EFLDRKVPANSFPLDGVFSFDHVDSTTNLLTRIYQPASLLHQTRHG TLELTKPLSTTEIVPVLIFFHGGSFTHSSANSAIYDTFCRRLVTIC GVVVVSVDYRRSPEHRYPCAYDDGWNALNWVKSRVWLQSGKDSNVY VYLAGDSSGGNIAHNVAVRATNEGVKVLGNILLHPMFGGQERTQSE KTLDGKYFVTIQDRDWYWRAYLPEGEDRDHPACNPFGPRGQSLKGV NFPKSLVVVAGLDLVQDWQLAYVDGLKKTGLEVNLLYLKQATIGFY FLPNNDHFHCLMEELNKFVHSIEDSQSKSSPVLLTP GID1C: (SEQ ID NO: 97) MAGSEEVNLIESKTVVPLNTWVLISNFKLAYNLLRRPDGTFNRHLA EFLDRKVPANANPVNGVFSFDVIIDRQTNLLSRVYRPADAGTSPSI TDLQNPVDGEIVPVIVFFHGGSFAHSSANSAIYDTLCRRLVGLCGA VVVSVNYRRAPENRYPCAYDDGWAVLKWVNSSSWLRSKKDSKVRIF LAGDSSGGNIVHNVAVRAVESRIDVLGNILLNPMFGGTERTESEKR LDGKYFVTVRDRDWYWRAFLPEGEDREHPACSPFGPRSKSLEGLSF PKSLVVVAGLDLIQDWQLKYAEGLKKAGQEVKLLYLEQATIGFYLL PNNNHFHTVMDEIAAFVNAECQ.

Dimerizers

Dimerizers (“dimerizing agents) that can provide for dimerization of a first member of a dimerizer-binding pair and a second member of a dimerizer-binding pair include, e.g. (where the dimerizer is in parentheses following the dimerizer-binding pair:

-   a) FKBP and FKBP (rapamycin); -   b) FKBP and CnA (rapamycin); -   c) FKBP and cyclophilin (rapamycin); -   d) FKBP and FRG (rapamycin); -   e) GyrB and GyrB (coumermycin); -   f) DHFR and DHFR (methotrexate); -   g) DmrB and DmrB (AP20187); -   h) PYL and ABI (abscisic acid); -   i) Cry2 and CIB1 (blue light); and -   j) GAI and GID1 (gibberellin).

As noted above, rapamycin can serve as a dimerizer. Alternatively, a rapamycin derivative or analog can be used. See, e.g., WO96/41865; WO 99/36553; WO 01/14387; and Ye et al (1999) Science 283:88-91. For example, analogs, homologs, derivatives and other compounds related structurally to rapamycin (”rapalogs“) include, among others, variants of rapamycin having one or more of the following modifications relative to rapamycin: demethylation, elimination or replacement of the methoxy at C7, C42 and/or C29; elimination, derivatization or replacement of the hydroxy at C13, C43 and/or C28; reduction, elimination or derivatization of the ketone at C14, C24 and/or C30; replacement of the 6-membered pipecolate ring with a 5-membered prolyl ring; and alternative substitution on the cyclohexyl ring or replacement of the cyclohexyl ring with a substituted cyclopentyl ring. Additional information is presented in, e.g., U.S. Pat. Nos. 5,525,610; 5,310,903 5,362,718; and 5,527,907. Selective epimerization of the C-28 hydroxyl group has been described; see, e.g., WO 01/14387. Additional synthetic dimerizing agents suitable for use as an alternative to rapamycin include those described in U.S. Patent Publication No. 2012/0130076.

Rapamycin has the structure:

Suitable rapalogs include, e.g.,

Also suitable as a rapalog is a compound of the formula:

where n is 1 or 2; R²⁸ and R⁴³ are independently H, or a substituted or unsubstituted aliphatic or acyl moiety; one of R^(7a) and R^(7b) is H and the other is halo, R^(A), OR^(A), SR^(A), −OC(O)R^(A), —OC(O)NR^(A)R^(B), —NR^(A)R^(B), —NR^(B)C(OR)R^(A), NR^(B)C(O)R^(A), —NR^(B)SO₂R^(A), or NR^(B)SO₂NR^(A)R^(B′); or R^(7a) and R^(7b), taken together, are H in the tetraene moiety:

where R^(A) is H or a substituted or unsubstituted aliphatic, heteroaliphatic, aryl, or heteroaryl moiety and where R^(B) and R^(B′) are independently H, OH, or a substituted or unsubstituted aliphatic, heteroaliphatic, aryl, or heteroaryl moiety.

As noted above, coumermycin can serve as a dimerizing agent. Alternatively, a coumermycin analog can be used. See, e.g., Farrar et al. (1996) Nature 383:178-181; and U.S. Pat. No. 6,916,846.

As noted above, in some cases, the dimerizing agent is methotrexate, e.g., a non-cytotoxic, homo-bifunctional methotrexate dimer. See, e.g., U.S. Pat. No. 8,236,925.

Intracellular Signaling Domain

Intracellular signaling domains suitable for use in a CAR of the present disclosure include any desired signaling domain that provides a distinct and detectable signal (e.g., increased production of one or more cytokines by the cell; change in transcription of a target gene; change in activity of a protein; change in cell behavior, e.g., cell death; cellular proliferation; cellular differentiation; cell survival; modulation of cellular signaling responses; etc.) in response to activation of the CAR (i.e., activated by antigen and dimerizing agent). In some embodiments, the intracellular signaling domain includes at least one (e.g., one, two, three, four, five, six, etc.) ITAM motifs as described below. In some embodiments, the intracellular signaling domain includes DAP10/CD28 type signaling chains. In some embodiments, the intracellular signaling domain is not covalently attached to the membrane bound CAR, but is instead diffused in the cytoplasm.

ITAM

Intracellular signaling domains suitable for use in a CAR of the present disclosure include immunoreceptor tyrosine-based activation motif (ITAM)-containing intracellular signaling polypeptides. An ITAM motif is YX₁X₂L/I, where X₁ and X₂ are independently any amino acid (SEQ ID NO:130). In some cases, the intracellular signaling domain of a subject CAR comprises 1, 2, 3, 4, or 5 ITAM motifs. In some cases, an ITAM motif is repeated twice in an intracellular signaling domain, where the first and second instances of the ITAM motif are separated from one another by 6 to 8 amino acids, e.g., (YX₁X₂L/I)(X₃)_(n)(YX₁X₂L/I), where n is an integer from 6 to 8, and each of the 6-8 X₃ can be any amino acid (SEQ ID NO:131). In some cases, the intracellular signaling domain of a subject CAR comprises 3 ITAM motifs.

A suitable intracellular signaling domain can be an ITAM motif-containing portion that is derived from a polypeptide that contains an ITAM motif. For example, a suitable intracellular signaling domain can be an ITAM motif-containing domain from any ITAM motif-containing protein. Thus, a suitable intracellular signaling domain need not contain the entire sequence of the entire protein from which it is derived. Examples of suitable ITAM motif-containing polypeptides include, but are not limited to: DAP12; FCER1G (Fc epsilon receptor I gamma chain); CD3D (CD3 delta); CD3E (CD3 epsilon); CD3G (CD3 gamma); CD3Z (CD3 zeta); and CD79A (antigen receptor complex-associated protein alpha chain).

In some cases, the intracellular signaling domain is derived from DAP12 (also known as TYROBP; TYRO protein tyrosine kinase binding protein; KARAP; PLOSL; DNAX-activation protein 12; KAR-associated protein; TYRO protein tyrosine kinase-binding protein; killer activating receptor associated protein; killer-activating receptor-associated protein; etc.). For example, a suitable intracellular signaling domain polypeptide can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100%, amino acid sequence identity to any of the following amino acid sequences (4 isoforms):

(SEQ ID NO: 98) MGGLEPCSRLLLLPLLLAVSGLRPVQAQAQSDCSCSTVSPGVLAGI VMGDLVLTVLIALAVYFLGRLVPRGRGAAEAATRKQRITETESP YQ EL QGQRSDV YSDL NTQRPYYK; (SEQ ID NO: 99) MGGLEPCSRLLLLPLLLAVSGLRPVQAQAQSDCSCSTVSPGVLAGI VMGDLVLTVLIALAVYFLGRLVPRGRGAAEATRKQRITETESP YQE L QGQRSDV YSDL NTQRPYYK; (SEQ ID NO: 100) MGGLEPCSRLLLLPLLLAVSDCSCSTVSPGVLAGIVMGDLVLTVLI ALAVYFLGRLVPRGRGAAEAATRKQRITETESP YQEL QGQRSDV YS DL NTQRPYYK; or (SEQ ID NO: 101) MGGLEPCSRLLLLPLLLAVSDCSCSTVSPGVLAGIVMGDLVLTVLI ALAVYFLGRLVPRGRGAAEATRKQRITETESP YQEL QGQRSDV YSD L NTQRPYYK, where the ITAM motifs are in bold and are underlined.

Likewise, a suitable intracellular signaling domain polypeptide can comprise an ITAM motif-containing portion of the full length DAP12 amino acid sequence. Thus, a suitable intracellular signaling domain polypeptide can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100%, amino acid sequence identity to the following amino acid sequence:

ESPYQELQGQRSDVYSDLNTQ (SEQ ID NO:102), where the ITAM motifs are in bold and are underlined.

In some cases, the intracellular signaling domain is derived from FCER1G (also known as FCRG; Fc epsilon receptor I gamma chain; Fc receptor gamma-chain; fc-epsilon RI-gamma; fcRgamma; fceRI gamma; high affinity immunoglobulin epsilon receptor subunit gamma; immunoglobulin E receptor, high affinity, gamma chain; etc.). For example, a suitable intracellular signaling domain polypeptide can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100% amino acid sequence identity to the following amino acid sequence:

MIPAVVLLLLLLVEQAAALGEPQLCYILDAILFLYGIVLTLLYCRLKIQVRKAAITSY EKSDGVYTGLSTRNQETYETLKHEKPPQ (SEQ ID NO:103), where the ITAM motifs are in bold and are underlined.

Likewise, a suitable intracellular signaling domain polypeptide can comprise an ITAM motif-containing portion of the full length FCER1G amino acid sequence. Thus, a suitable intracellular signaling domain polypeptide can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100%, amino acid sequence identity to the following amino acid sequence:

DGVYTGLSTRNQETYETLKHE (SEQ ID NO:104), where the ITAM motifs are in bold and are underlined.

In some cases, the intracellular signaling domain is derived from T-cell surface glycoprotein CD3 delta chain (also known as CD3D; CD3-DELTA; T3D; CD3 antigen, delta subunit; CD3 delta; CD3d antigen, delta polypeptide (TiT3 complex); OKT3, delta chain; T-cell receptor T3 delta chain; T-cell surface glycoprotein CD3 delta chain; etc.). For example, a suitable intracellular signaling domain polypeptide can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100%, amino acid sequence identity to a contiguous stretch of from about 100 amino acids to about 110 amino acids (aa), from about 110 aa to about 115 aa, from about 115 aa to about 120 aa, from about 120 aa to about 130 aa, from about 130 aa to about 140 aa, from about 140 aa to about 150 aa, or from about 150 aa to about 170 aa, of either of the following amino acid sequences (2 isoforms):

MEHSTFLSGLVLATLLSQVSPFKIPIEELEDRVFVNCNTSITWVEGTVGTLLSDITRL DLGKRILDPRGIYRCNGTDIYKDKESTVQVHYRMCQSCVELDPATVAGIIVTDVIAT LLLALGVFCFAGHETGRLSGAADTQALLRNDQVYQPLRDRDDAQYSHLGGNWAR NK (SEQ ID NO:105) or

MEHSTFLSGLVLATLLSQVSPFKIPIEELEDRVFVNCNTSITWVEGTVGTLLSDITRL DLGKRILDPRGIYRCNGTDIYKDKESTVQVHYRTADTQALLRNDQVYQPLRDRDD AQYSHLGGNWARNK (SEQ ID NO:106), where the ITAM motifs are in bold and are underlined.

Likewise, a suitable intracellular signaling domain polypeptide can comprise an ITAM motif-containing portion of the full length CD3 delta amino acid sequence. Thus, a suitable intracellular signaling domain polypeptide can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100%, amino acid sequence identity to the following amino acid sequence:

DQVYQPLRDRDDAQYSHLGGN (SEQ ID NO:107), where the ITAM motifs are in bold and are underlined.

In some cases, the intracellular signaling domain is derived from T-cell surface glycoprotein CD3 epsilon chain (also known as CD3e, T-cell surface antigen T3/Leu-4 epsilon chain, T-cell surface glycoprotein CD3 epsilon chain, AI504783, CD3, CD3epsilon, T3e, etc.). For example, a suitable intracellular signaling domain polypeptide can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100%, amino acid sequence identity to a contiguous stretch of from about 100 amino acids to about 110 amino acids (aa), from about 110 aa to about 115 aa, from about 115 aa to about 120 aa, from about 120 aa to about 130 aa, from about 130 aa to about 140 aa, from about 140 aa to about 150 aa, or from about 150 aa to about 205 aa, of the following amino acid sequence:

MQSGTHWRVLGLCLLSVGVWGQDGNEEMGGITQTPYKVSISGTTVILTCPQYPGSE ILWQHNDKNIGGDEDDKNIGSDEDHLSLKEFSELEQSGYYVCYPRGSKPEDANFYL YLRARVCENCMEMDVMSVATIVIVDICITGGLLLLVYYWSKNRKAKAKPVTRGAG AGGRQRGQNKERPPPVPNPDYEPIRKGQRDLYSGLNQRRI (SEQ ID NO:108), where the ITAM motifs are in bold and are underlined.

Likewise, a suitable intracellular signaling domain polypeptide can comprise an ITAM motif-containing portion of the full length CD3 epsilon amino acid sequence. Thus, a suitable intracellular signaling domain polypeptide can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100%, amino acid sequence identity to the following amino acid sequence:

NPDYEPIRKGQRDLYSGLNQR (SEQ ID NO:109), where the ITAM motifs are in bold and are underlined.

In some cases, the intracellular signaling domain is derived from T-cell surface glycoprotein CD3 gamma chain (also known as CD3G, T-cell receptor T3 gamma chain, CD3-GAMMA, T3G, gamma polypeptide (TiT3 complex), etc.). For example, a suitable intracellular signaling domain polypeptide can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100%, amino acid sequence identity to a contiguous stretch of from about 100 amino acids to about 110 amino acids (aa), from about 110 aa to about 115 aa, from about 115 aa to about 120 aa, from about 120 aa to about 130 aa, from about 130 aa to about 140 aa, from about 140 aa to about 150 aa, or from about 150 aa to about 180 aa, of the following amino acid sequence:

MEQGKGLAVLILAIILLQGTLAQSIKGNHLVKVYDYQEDGSVLLTCDAEAKNITWF KDGKMIGFLTEDKKKWNLGSNAKDPRGMYQCKGSQNKSKPLQVYYRMCQNCIEL NAATISGFLFAEIVSIFVLAVGVYFIAGQDGVRQSRASDKQTLLPNDQLYQPLKDRE DDQYSHLQGNQLRRN (SEQ ID NO:110), where the ITAM motifs are in bold and are underlined.

Likewise, a suitable intracellular signaling domain polypeptide can comprise an ITAM motif-containing portion of the full length CD3 gamma amino acid sequence. Thus, a suitable intracellular signaling domain polypeptide can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100%, amino acid sequence identity to the following amino acid sequence:

DQLYQPLKDREDDQYSHLQGN (SEQ ID NO:111), where the ITAM motifs are in bold and are underlined.

In some cases, the intracellular signaling domain is derived from T-cell surface glycoprotein CD3 zeta chain (also known as CD3Z, T-cell receptor T3 zeta chain, CD247, CD3-ZETA, CD3H, CD3Q, T3Z, TCRZ, etc.). For example, a suitable intracellular signaling domain polypeptide can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100%, amino acid sequence identity to a contiguous stretch of from about 100 amino acids to about 110 amino acids (aa), from about 110 aa to about 115 aa, from about 115 aa to about 120 aa, from about 120 aa to about 130 aa, from about 130 aa to about 140 aa, from about 140 aa to about 150 aa, or from about 150 aa to about 160 aa, of either of the following amino acid sequences (2 isoforms):

MKWKALFTAAILQAQLPITEAQSFGLLDPKLCYLLDGILFIYGVILTALFLRVKFSRS ADAPAYQQGQNQLYNELNLGRREEYDVLDKRRGRDPEMGGKPRRKNPQEGLYN ELQKDKMAEAYSEIGMKGERRRGKGHDGLYQGLSTATKDTYDALHMQALPPR (SEQ ID NO:112) or

MKWKALFTAAILQAQLPITEAQSFGLLDPKLCYLLDGILFIYGVILTALFLRVKFSRS ADAPAYQQGQNQLYNELNLGRREEYDVLDKRRGRDPEMGGKPQRRKNPQEGLY NELQKDKMAEAYSEIGMKGERRRGKGHDGLYQGLSTATKDTYDALHMQALPPR(SEQ ID NO:113) , where the ITAM motifs are in bold and are underlined.

Likewise, a suitable intracellular signaling domain polypeptide can comprise an ITAM motif-containing portion of the full length CD3 zeta amino acid sequence. Thus, a suitable intracellular signaling domain polypeptide can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100%, amino acid sequence identity to any of the following amino acid sequences:

RVKFSRSADAPAYQQGQNQLYNELNLGRREEYDVLDKRRGRDPEMGGKPRRKNP QEGLYNELQKDKMAEAYSEIGMKGERRRGKGHDGLYQGLSTATKDTYDALHMQ ALPPR (SEQ ID NO:18); NQLYNELNLGRREEYDVLDKR (SEQ ID NO:114); EGLYNELQKDKMAEAYSEIGMK (SEQ ID NO:115); or

DGLYQGLSTATKDTYDALHMQ (SEQ ID NO:116), where the ITAM motifs are in bold and are underlined.

In some cases, the intracellular signaling domain is derived from CD79A (also known as B-cell antigen receptor complex-associated protein alpha chain; CD79a antigen (immunoglobulin-associated alpha); MB-1 membrane glycoprotein; ig-alpha; membrane-bound immunoglobulin-associated protein; surface IgM-associated protein; etc.). For example, a suitable intracellular signaling domain polypeptide can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100%, amino acid sequence identity to a contiguous stretch of from about 100 amino acids to about 110 amino acids (aa), from about 110 aa to about 115 aa, from about 115 aa to about 120 aa, from about 120 aa to about 130 aa, from about 130 aa to about 150 aa, from about 150 aa to about 200 aa, or from about 200 aa to about 220 aa, of either of the following amino acid sequences (2 isoforms):

MPGGPGVLQALPATIFLLFLLSAVYLGPGCQALWMHKVPASLMVSLGEDA HFQCPHNSSNNANVTWWRVLHGNYTWPPEFLGPGEDPNGTLIIQNVNKSHGGIYV CRVQEGNESYQQSCGTYLRVRQPPPRPFLDMGEGTKNRIITAEGIILLFCAVVPGTLL LFRKRWQNEKLGLDAGDEYEDENLYEGLNLDDCSMYEDISRGLQGTYQDVGSLN IGDVQLEKP (SEQ ID NO:117); or

MPGGPGVLQALPATIFLLFLLSAVYLGPGCQALWMHKVPASLMVSLGEDA HFQCPHNSSNNANVTWWRVLHGNYTWPPEFLGPGEDPNEPPPRPFLDMGEGTKNR IITAEGIILLFCAVVPGTLLLFRKRWQNEKLGLDAGDEYEDENLYEGLNLDDCSMYE DISRGLQGTYQDVGSLNIGDVQLEKP (SEQ ID NO:118), where the ITAM motifs are in bold and are underlined.

Likewise, a suitable intracellular signaling domain polypeptide can comprise an ITAM motif-containing portion of the full length CD79A amino acid sequence. Thus, a suitable intracellular signaling domain polypeptide can comprise an amino acid sequence having at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 98%, or 100%, amino acid sequence identity to the following amino acid sequence: ENLYEGLNLDDCSMYEDISRG (SEQ ID NO:119), where the ITAM motifs are in bold and are underlined.

DAP10/CD28

Intracellular signaling domains suitable for use in a CAR of the present disclosure include a DAP10/CD28 type signaling chain.

An example of a DAP10 signaling chain is the amino acid sequence is:

RPRRSPAQDGKVYINMPGRG (SEQ ID NO:120). In some embodiments, a suitable intracellular signaling domain comprises an amino acid sequence having at least about 85%, at least about 90%, at least about 95%, at least about 98%, or at least about 99%, amino acid sequence identity to the entire length of the amino acid sequence

RPRRSPAQDGKVYINMPGRG (SEQ ID NO:120).

An example of a CD28 signaling chain is the amino acid sequence is

FWVLVVVGGVLACYSLLVTVAFIIFWVRSKRSRLLHSDYMNMTPRRPGPTRKHYQ PYAPPRDFAAYRS (SEQ ID NO:121). In some embodiments, a suitable intracellular signaling domain comprises an amino acid sequence having at least about 85%, at least about 90%, at least about 95%, at least about 98%, or at least about 99%, amino acid sequence identity to the entire length of the amino acid sequence

(SEQ ID NO: 121) FWVLVVVGGVLACYSLLVTVAFIIFWVRSKRSRLLHSD YMNM TPRR PGPTRKHYQPYAPPRDFAAYRS.

ZAP70

Intracellular signaling domains suitable for use in a CAR of the present disclosure include a ZAP70 polypeptide, e.g., a polypeptide comprising an amino acid sequence having at least about 85%, at least about 90%, at least about 95%, at least about 98%, at least about 99%, or 100%, amino acid sequence identity to a contiguous stretch of from about 300 amino acids to about 400 amino acids, from about 400 amino acids to about 500 amino acids, or from about 500 amino acids to 619 amino acids, of the following amino acid sequence:

(SEQ ID NO: 36) MPDPAAHLPFFYGSISRAEAEEHLKLAGMADGLFLLRQCLRSLGGY VLSLVHDVRFHHFPIERQLNGTYAIAGGKAHCGPAELCEFYSRDPD GLPCNLRKPCNRPSGLEPQPGVFDCLRDAMVRDYVRQTWKLEGEAL EQAIISQAPQVEKLIATTAHERMPWYHSSLTREEAERKLYSGAQTD GKFLLRPRKEQGTYALSLIYGKTVYHYLISQDKAGKYCIPEGTKFD TLWQLVEYLKLKADGLIYCLKEACPNSSASNASGAAAPTLPAHPST LTHPQRRIDTLNSDGYTPEPARITSPDKPRPMPMDTSVYESPYSDP EELKDKKLFLKRDNLLIADIELGCGNFGSVRQGVYRMRKKQIDVAI KVLKQGTEKADTEEMMREAQIIVIHQLDNPYIVRLIGVCQAEALML VMEMAGGGPLHKFLVGKREEIPVSNVAELLHQVSMGMKYLEEKNFV HRDLAARNVLLVNRHYAKISDFGLSKALGADDSYYTARSAGKWPLK WYAPECINFRKFSSRSDVWSYGVTMWEALSYGQKPYKKMKGPEVMA FIEQGKRMECPPECPPELYALMSDCWIYKWEDRPDFLTVEQRMRAC YYSLASKVEGPPGSTQKAEAACA.

Additional Sequences

The first and/or the second polypeptide of a subject CAR can further include one or more additional polypeptide domains, where such domains include, but are not limited to, a signal sequence; an epitope tag; an affinity domain; and a polypeptide that produces a detectable signal.

Signal Sequences

Signal sequences that are suitable for use in a subject CAR, e.g., in the first polypeptide of a subject CAR, include any eukaryotic signal sequence, including a naturally-occurring signal sequence, a synthetic (e.g., man-made) signal sequence, etc.

Epitope Tag

Suitable epitope tags include, but are not limited to, hemagglutinin (HA; e.g., YPYDVPDYA (SEQ ID NO:122); FLAG (e.g., DYKDDDDK (SEQ ID NO:123); c-myc (e.g., EQKLISEEDL; SEQ ID NO:4), and the like.

Affinity Domain

Affinity domains include peptide sequences that can interact with a binding partner, e.g., such as one immobilized on a solid support, useful for identification or purification. DNA sequences encoding multiple consecutive single amino acids, such as histidine, when fused to the expressed protein, may be used for one-step purification of the recombinant protein by high affinity binding to a resin column, such as nickel sepharose. Exemplary affinity domains include His5 (HHHHH) (SEQ ID NO:124), HisX6 (HHHHHH) (SEQ ID NO:125), C-myc (EQKLISEEDL) (SEQ ID NO:4), Flag (DYKDDDDK) (SEQ ID NO:123), StrepTag (WSHPQFEK) (SEQ ID NO:126), hemagluttinin, e.g., HA Tag (YPYDVPDYA) (SEQ ID NO:122), GST, thioredoxin, cellulose binding domain, RYIRS (SEQ ID NO:127), Phe-His-His-Thr (SEQ ID NO:128), chitin binding domain, S-peptide, T7 peptide, SH2 domain, C-end RNA tag, WEAAAREACCRECCARA (SEQ ID NO:129), metal binding domains, e.g., zinc binding domains or calcium binding domains such as those from calcium-binding proteins, e.g., calmodulin, troponin C, calcineurin B, myosin light chain, recoverin, S-modulin, visinin, VILIP, neurocalcin, hippocalcin, frequenin, caltractin, calpain large-subunit, S100 proteins, parvalbumin, calbindin D9K, calbindin D28K, and calretinin, inteins, biotin, streptavidin, MyoD, Id, leucine zipper sequences, and maltose binding protein.

Detectable Signal-Producing Polypeptides

Suitable detectable signal-producing proteins include, e.g., fluorescent proteins; enzymes that catalyze a reaction that generates a detectable signal as a product; and the like.

Suitable fluorescent proteins include, but are not limited to, green fluorescent protein (GFP) or variants thereof, blue fluorescent variant of GFP (BFP), cyan fluorescent variant of GFP (CFP), yellow fluorescent variant of GFP (YFP), enhanced GFP (EGFP), enhanced CFP (ECFP), enhanced YFP (EYFP), GFPS65T, Emerald, Topaz (TYFP), Venus, Citrine, mCitrine, GFPuv, destabilised EGFP (dEGFP), destabilised ECFP (dECFP), destabilised EYFP (dEYFP), mCFPm, Cerulean, T-Sapphire, CyPet, YPet, mKO, HcRed, t-HcRed, DsRed, DsRed2, DsRed-monomer, J-Red, dimer2, t-dimer2(12), mRFP1, pocilloporin, Renilla GFP, Monster GFP, paGFP, Kaede protein and kindling protein, Phycobiliproteins and Phycobiliprotein conjugates including B-Phycoerythrin, R-Phycoerythrin and Allophycocyanin. Other examples of fluorescent proteins include mHoneydew, mBanana, mOrange, dTomato, tdTomato, mTangerine, mStrawberry, mCherry, mGrape1, mRaspberry, mGrape2, mPlum (Shaner et al. (2005) Nat. Methods 2:905-909), and the like. Any of a variety of fluorescent and colored proteins from Anthozoan species, as described in, e.g., Matz et al. (1999) Nature Biotechnol. 17:969-973, is suitable for use.

Suitable enzymes include, but are not limited to, horse radish peroxidase (HRP), alkaline phosphatase (AP), beta-galactosidase (GAL), glucose-6-phosphate dehydrogenase, beta-N-acetylglucosaminidase, β-glucuronidase, invertase, Xanthine Oxidase, firefly luciferase, glucose oxidase (GO), and the like.

Recombination of Sequences

In certain instances, sequences of the polypeptides of a CAR, e.g., CAR domains, may be rearranged or deleted in a cell through the use of site-specific recombination technology. In certain embodiments, the cellular activation-related response to a particular CAR can be changed by site-specific recombination, e.g., a first intracellular signaling domain of a CAR eliciting a first activation-related response may be exchanged for a second intracellular signaling domain eliciting a second activation-related response. In certain instances, the response to a particular dimerizer of a CAR can be changed by site-specific recombination, e.g., a first dimerizer-binding pair causing the dimerization of a CAR in the presence of a first dimerizer may be exchanged for a second dimerizer-binding pair causing the dimerization of the CAR in the presence of a second dimerizer. As will be clear to one skilled in the art, site-specific recombination can be used in a cell to exchange any domain or sequence of a CAR with any other domain or sequence as disclosed herein. As will also be clear to one skilled in the art, site-specific recombination can be used in a cell to delete any domain or sequence of a CAR. Such exchange and excision of sequences and domains is known in the art, see, e.g., domain switching in signalobodies as described in Tone et al. (2013) Biotechnology and Bioengineering, 3219-3226, the disclosure of which is disclosed herein by reference. Mechanisms and requirements for performing site-specific recombination in vivo are also well known in the art, see, e.g., Grindley et al. (2006) Annual Review of Biochemistry, 567-605 and Tropp (2012) Molecular Biology (Jones & Bartlett Publishers, Sudbury, Mass.), the disclosures of which are incorporated herein by reference.

Nucleic Acids

The present disclosure provides a nucleic acid that comprises a nucleotide sequence encoding the first and/or the second polypeptide of a heterodimeric, conditionally active CAR of the present disclosure. A nucleic acid comprising a nucleotide sequence encoding the first and/or the second polypeptide of a heterodimeric, conditionally active CAR of the present disclosure will in some embodiments be DNA, including, e.g., a recombinant expression vector. A nucleic acid comprising a nucleotide sequence encoding the first and/or the second polypeptide of a heterodimeric, conditionally active CAR of the present disclosure will in some embodiments be RNA, e.g., in vitro synthesized RNA.

In some cases, a nucleic acid of the present disclosure comprises a nucleotide sequence encoding only the first polypeptide (and not the second polypeptide) of a heterodimeric, conditionally active CAR of the present disclosure. In some cases, a nucleic acid of the present disclosure comprises a nucleotide sequence encoding only the second polypeptide (and not the first polypeptide) of a heterodimeric, conditionally active CAR of the present disclosure. In some cases, a nucleic acid of the present disclosure comprises a nucleotide sequence encoding both the first polypeptide and the second polypeptide of a heterodimeric, conditionally active CAR of the present disclosure.

In some cases, a subject nucleic acid provides for production of a CAR of the present disclosure, e.g., in a mammalian cell. In other cases, a subject nucleic acid provides for amplification of the CAR-encoding nucleic acid.

A nucleotide sequence encoding the first and/or the second polypeptide of a CAR of the present disclosure can be operably linked to a transcriptional control element, e.g., a promoter, and enhancer, etc.

Suitable promoter and enhancer elements are known in the art. For expression in a bacterial cell, suitable promoters include, but are not limited to, lacI, lacZ, T3, T7, gpt, lambda P and trc. For expression in a eukaryotic cell, suitable promoters include, but are not limited to, light and/or heavy chain immunoglobulin gene promoter and enhancer elements; cytomegalovirus immediate early promoter; herpes simplex virus thymidine kinase promoter; early and late SV40 promoters; promoter present in long terminal repeats from a retrovirus; mouse metallothionein-I promoter; and various art-known tissue specific promoters.

Suitable reversible promoters, including reversible inducible promoters are known in the art. Such reversible promoters may be isolated and derived from many organisms, e.g., eukaryotes and prokaryotes. Modification of reversible promoters derived from a first organism for use in a second organism, e.g., a first prokaryote and a second a eukaryote, a first eukaryote and a second a prokaryote, etc., is well known in the art. Such reversible promoters, and systems based on such reversible promoters but also comprising additional control proteins, include, but are not limited to, alcohol regulated promoters (e.g., alcohol dehydrogenase I (a1cA) gene promoter, promoters responsive to alcohol transactivator proteins (A1cR), etc.), tetracycline regulated promoters, (e.g., promoter systems including TetActivators, TetON, TetOFF, etc.), steroid regulated promoters (e.g., rat glucocorticoid receptor promoter systems, human estrogen receptor promoter systems, retinoid promoter systems, thyroid promoter systems, ecdysone promoter systems, mifepristone promoter systems, etc.), metal regulated promoters (e.g., metallothionein promoter systems, etc.), pathogenesis-related regulated promoters (e.g., salicylic acid regulated promoters, ethylene regulated promoters, benzothiadiazole regulated promoters, etc.), temperature regulated promoters (e.g., heat shock inducible promoters (e.g., HSP-70, HSP-90, soybean heat shock promoter, etc.), light regulated promoters, synthetic inducible promoters, and the like.

In some instances, the locus or construct or transgene containing the suitable promoter is irreversibly switched through the induction of an inducible system. Suitable systems for induction of an irreversible switch are well known in the art, e.g., induction of an irreversible switch may make use of a Cre-lox-mediated recombination (see, e.g., Fuhrmann-Benzakein, et al., PNAS (2000) 28:e99, the disclosure of which is incorporated herein by reference). Any suitable combination of recombinase, endonuclease, ligase, recombination sites, etc. known to the art may be used in generating an irreversibly switchable promoter. Methods, mechanisms, and requirements for performing site-specific recombination, described elsewhere herein, find use in generating irreversibly switched promoters and are well known in the art, see, e.g., Grindley et al. (2006) Annual Review of Biochemistry, 567-605 and Tropp (2012) Molecular Biology (Jones & Bartlett Publishers, Sudbury, Mass.), the disclosures of which are incorporated herein by reference.

In some cases, the promoter is a CD8 cell-specific promoter, a CD4 cell-specific promoter, a neutrophil-specific promoter, or an NK-specific promoter. For example, a CD4 gene promoter can be used; see, e.g., Salmon et al. (1993) Proc. Natl. Acad. Sci. USA 90:7739; and Marodon et al. (2003) Blood 101:3416. As another example, a CD8 gene promoter can be used. NK cell-specific expression can be achieved by use of an Ncr1 (p46) promoter; see, e.g., Eckelhart et al. (2011) Blood 117:1565.

In some embodiments, e.g., for expression in a yeast cell, a suitable promoter is a constitutive promoter such as an ADH1 promoter, a PGK1 promoter, an ENO promoter, a PYK1 promoter and the like; or a regulatable promoter such as a GAL1 promoter, a GAL10 promoter, an ADH2 promoter, a PHOS promoter, a CUP1 promoter, a GALT promoter, a MET25 promoter, a MET3 promoter, a CYC1 promoter, a HIS3 promoter, an ADH1 promoter, a PGK promoter, a GAPDH promoter, an ADC1 promoter, a TRP1 promoter, a URA3 promoter, a LEU2 promoter, an ENO promoter, a TP1 promoter, and AOX1 (e.g., for use in Pichia). Selection of the appropriate vector and promoter is well within the level of ordinary skill in the art.

Suitable promoters for use in prokaryotic host cells include, but are not limited to, a bacteriophage T7 RNA polymerase promoter; a trp promoter; a lac operon promoter; a hybrid promoter, e.g., a lac/tac hybrid promoter, a tac/trc hybrid promoter, a trp/lac promoter, a T7/lac promoter; a trc promoter; a tac promoter, and the like; an araBAD promoter; in vivo regulated promoters, such as an ssaG promoter or a related promoter (see, e.g., U.S. Patent Publication No. 20040131637), a pagC promoter (Pulkkinen and Miller, J. Bacteriol., 1991: 173(1): 86-93; Alpuche-Aranda et al., PNAS, 1992; 89(21): 10079-83), a nirB promoter (Harborne et al. (1992) Mol. Micro. 6:2805-2813), and the like (see, e.g., Dunstan et al. (1999) Infect. Immun. 67:5133-5141; McKelvie et al. (2004) Vaccine 22:3243-3255; and Chatfield et al. (1992) Biotechnol. 10:888-892); a sigma70 promoter, e.g., a consensus sigma70 promoter (see, e.g., GenBank Accession Nos. AX798980, AX798961, and AX798183); a stationary phase promoter, e.g., a dps promoter, an spv promoter, and the like; a promoter derived from the pathogenicity island SPI-2 (see, e.g., WO96/17951); an actA promoter (see, e.g., Shetron-Rama et al. (2002) Infect. Immun. 70:1087-1096); an rpsM promoter (see, e.g., Valdivia and Falkow (1996). Mol. Microbiol. 22:367); a tet promoter (see, e.g., Hillen, W. and Wissmann, A. (1989) In Saenger, W. and Heinemann, U. (eds), Topics in Molecular and Structural Biology, Protein—Nucleic Acid Interaction. Macmillan, London, UK, Vol. 10, pp. 143-162); an SP6 promoter (see, e.g., Melton et al. (1984) Nucl. Acids Res. 12:7035); and the like. Suitable strong promoters for use in prokaryotes such as Escherichia coli include, but are not limited to Trc, Tac, T5, T7, and P_(Lambda). Non-limiting examples of operators for use in bacterial host cells include a lactose promoter operator (LacI repressor protein changes conformation when contacted with lactose, thereby preventing the Lad repressor protein from binding to the operator), a tryptophan promoter operator (when complexed with tryptophan, TrpR repressor protein has a conformation that binds the operator; in the absence of tryptophan, the TrpR repressor protein has a conformation that does not bind to the operator), and a tac promoter operator (see, for example, deBoer et al. (1983) Proc. Natl. Acad. Sci. U.S.A. 80:21-25).

A nucleotide sequence encoding a subject CAR can be present in an expression vector and/or a cloning vector. Where a subject CAR comprises two separate polypeptides, nucleotide sequences encoding the two polypeptides can be cloned in the same or separate vectors. An expression vector can include a selectable marker, an origin of replication, and other features that provide for replication and/or maintenance of the vector. Suitable expression vectors include, e.g., plasmids, viral vectors, and the like.

Large numbers of suitable vectors and promoters are known to those of skill in the art; many are commercially available for generating a subject recombinant constructs. The following vectors are provided by way of example. Bacterial: pBs, phagescript, PsiX174, pBluescript SK, pBs KS, pNH8a, pNH16a, pNH18a, pNH46a (Stratagene, La Jolla, Calif., USA); pTrc99A, pKK223-3, pKK233-3, pDR540, and pRIT5 (Pharmacia, Uppsala, Sweden). Eukaryotic: pWLneo, pSV2cat, pOG44, PXR1, pSG (Stratagene) pSVK3, pBPV, pMSG and pSVL (Pharmacia).

Expression vectors generally have convenient restriction sites located near the promoter sequence to provide for the insertion of nucleic acid sequences encoding heterologous proteins. A selectable marker operative in the expression host may be present. Suitable expression vectors include, but are not limited to, viral vectors (e.g. viral vectors based on vaccinia virus; poliovirus; adenovirus (see, e.g., Li et al., Invest Opthalmol Vis Sci 35:2543 2549, 1994; Borras et al., Gene Ther 6:515 524, 1999; Li and Davidson, PNAS 92:7700 7704, 1995; Sakamoto et al., H Gene Ther 5:1088 1097, 1999; WO 94/12649, WO 93/03769; WO 93/19191; WO 94/28938; WO 95/11984 and WO 95/00655); adeno-associated virus (see, e.g., Ali et al., Hum Gene Ther 9:81 86, 1998, Flannery et al., PNAS 94:6916 6921, 1997; Bennett et al., Invest Opthalmol Vis Sci 38:2857 2863, 1997; Jomary et al., Gene Ther 4:683 690, 1997, Rolling et al., Hum Gene Ther 10:641 648, 1999; Ali et al., Hum Mol Genet 5:591 594, 1996; Srivastava in WO 93/09239, Samulski et al., J. Vir. (1989) 63:3822-3828; Mendelson et al., Virol. (1988) 166:154-165; and Flotte et al., PNAS (1993) 90:10613-10617); SV40; herpes simplex virus; human immunodeficiency virus (see, e.g., Miyoshi et al., PNAS 94:10319 23, 1997; Takahashi et al., J Virol 73:7812 7816, 1999); a retroviral vector (e.g., Murine Leukemia Virus, spleen necrosis virus, and vectors derived from retroviruses such as Rous Sarcoma Virus, Harvey Sarcoma Virus, avian leukosis virus, human immunodeficiency virus, myeloproliferative sarcoma virus, and mammary tumor virus); and the like.

As noted above, in some embodiments, a nucleic acid comprising a nucleotide sequence encoding the first and/or the second polypeptide of a heterodimeric, conditionally active CAR of the present disclosure will in some embodiments be RNA, e.g., in vitro synthesized RNA. Methods for in vitro synthesis of RNA are known in the art; any known method can be used to synthesize RNA comprising a nucleotide sequence encoding the first and/or the second polypeptide of a heterodimeric, conditionally active CAR of the present disclosure. Methods for introducing RNA into a host cell are known in the art. See, e.g., Zhao et al. (2010) Cancer Res. 15:9053. Introducing RNA comprising a nucleotide sequence encoding the first and/or the second polypeptide of a heterodimeric, conditionally active CAR of the present disclosure into a host cell can be carried out in vitro or ex vivo or in vivo. For example, a host cell (e.g., an NK cell, a cytotoxic T lymphocyte, etc.) can be electroporated in vitro or ex vivo with RNA comprising a nucleotide sequence encoding the first and/or the second polypeptide of a heterodimeric, conditionally active CAR of the present disclosure.

Cells

The present disclosure provides a mammalian cell that is genetically modified to produce a heterodimeric, conditionally active CAR of the present disclosure.

Suitable mammalian cells include primary cells and immortalized cell lines. Suitable mammalian cell lines include human cell lines, non-human primate cell lines, rodent (e.g., mouse, rat) cell lines, and the like. Suitable mammalian cell lines include, but are not limited to, HeLa cells (e.g., American Type Culture Collection (ATCC) No. CCL-2), CHO cells (e.g., ATCC Nos. CRL9618, CCL61, CRL9096), 293 cells (e.g., ATCC No. CRL-1573), Vero cells, NIH 3T3 cells (e.g., ATCC No. CRL-1658), Huh-7 cells, BHK cells (e.g., ATCC No. CCL10), PC12 cells (ATCC No. CRL1721), COS cells, COS-7 cells (ATCC No. CRL1651), RAT1 cells, mouse L cells (ATCC No. CCLI.3), human embryonic kidney (HEK) cells (ATCC No. CRL1573), HLHepG2 cells, Hut-78, Jurkat, HL-60, NK cell lines (e.g., NKL, NK92, and YTS), and the like.

In some instances, the cell is not an immortalized cell line, but is instead a cell (e.g., a primary cell) obtained from an individual. For example, in some cases, the cell is an immune cell obtained from an individual. As an example, the cell is a T lymphocyte obtained from an individual. As another example, the cell is a cytotoxic cell obtained from an individual. As another example, the cell is a stem cell or progenitor cell obtained from an individual.

Methods of Activating an Immune Cell

The present disclosure provides methods of activating an immune cell in vitro, in vivo, or ex vivo. The methods generally involve contacting an immune cell (in vitro, in vivo, or ex vivo) with a dimerizing agent and an antigen, where the immune cell is genetically modified to produce a heterodimeric, conditionally active CAR of the present disclosure. In the presence of the dimerizing agent and the antigen, the heterodimeric, conditionally active CAR dimerizes and activates the immune cell, thereby producing an activated immune cell. Immune cells include, e.g., a cytotoxic T lymphocyte, an NK cell, a CD4⁺ T cell, a T regulatory (Treg) cell, etc.

Contacting the genetically modified immune cell (e.g., a T lymphocyte, an NK cell) with a dimerizing agent and a second member of a specific binding pair (e.g., an antigen, a ligand, a receptor) can increase production of a cytokine by the immune cell by at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 40%, at least about 50%, at least about 75%, at least about 2-fold, at least about 2.5-fold, at least about 5-fold, at least about 10-fold, or more than 10-fold, compared with the amount of cytokine produced by the immune cell in the absence of the second member of a specific binding pair and/or the dimerizing agent. Cytokines whose production can be increased include, but are not limited to, IL-2 and IFN-γ.

Contacting the genetically modified immune cell (e.g., a T lymphocyte, an NK cell) with a dimerizing agent and an antigen can increase production of a cytokine by the immune cell by at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 40%, at least about 50%, at least about 75%, at least about 2-fold, at least about 2.5-fold, at least about 5-fold, at least about 10-fold, or more than 10-fold, compared with the amount of cytokine produced by the immune cell in the absence of the antigen and/or the dimerizing agent. Cytokines whose production can be increased include, but are not limited to, IL-2 and IFN-γ.

Contacting a genetically modified cytotoxic cell (e.g., cytotoxic T lymphocyte) with a dimerizing agent and a second member of a specific binding pair (e.g., an antigen, a ligand, a receptor) can increase cytotoxic activity of the cytotoxic cell by at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 40%, at least about 50%, at least about 75%, at least about 2-fold, at least about 2.5-fold, at least about 5-fold, at least about 10-fold, or more than 10-fold, compared to the cytotoxic activity of the cytotoxic cell in the absence of the dimerizing agent.

Contacting a genetically modified cytotoxic cell (e.g., cytotoxic T lymphocyte) with a dimerizing agent and an antigen can increase cytotoxic activity of the cytotoxic cell by at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 40%, at least about 50%, at least about 75%, at least about 2-fold, at least about 2.5-fold, at least about 5-fold, at least about 10-fold, or more than 10-fold, compared to the cytotoxic activity of the cytotoxic cell in the absence of the dimerizing agent.

In other embodiments, e.g., depending on the host immune cell, contacting a genetically modified host cell with a dimerizing agent and an antigen can increase or decrease cell proliferation, cell survival, cell death, and the like.

Methods of Generating a Conditionally Activatable Cell

The present disclosure provides a method of generating a conditionally activatable cell. The method generally involves genetically modifying a mammalian cell with an expression vector, or an RNA (e.g., in vitro transcribed RNA), comprising nucleotide sequences encoding a heterodimeric, conditionally active CAR of the present disclosure. The genetically modified cell is conditionally activatable in the presence of: a) an antigen to which the first polypeptide of the CAR binds; and b) a dimerizer (a dimerizing agent). The genetic modification can be carried out in vivo, in vitro, or ex vivo. The cell can be an immune cell (e.g., a T lymphocyte or NK cell), a stem cell, a progenitor cell, etc.

In some cases, the genetic modification is carried out ex vivo. For example, a T lymphocyte, a stem cell, or an NK cell is obtained from an individual; and the cell obtained from the individual is genetically modified to express a CAR of the present disclosure. The genetically modified cell is conditionally activatable in the presence of: a) an antigen to which the first polypeptide of the CAR binds; and b) a dimerizer. In some cases, the genetically modified cell is activated ex vivo. In other cases, the genetically modified cell is introduced into an individual (e.g., the individual from whom the cell was obtained); and the genetically modified cell is activated in vivo, e.g., by administering to the individual a dimerizer. For example, where the antigen is present on the surface of a cell in the individual, there is no need to administer the antigen. The genetically modified cell comes into contact with the antigen present on the surface of a cell in the individual; and, upon administration to the individual of a dimerizer, the genetically modified cell is activated. For example, where the genetically modified cell is a T lymphocyte, the genetically modified cell can exhibit cytotoxicity toward a cell that presents an antigen on its surface to which the CAR binds.

Treatment Methods

The present disclosure provides various treatment methods using a subject CAR.

Cytotoxicity Methods

A CAR of the present disclosure, when present in a T lymphocyte or an NK cell, can mediate cytotoxicity toward a target cell. A CAR of the present disclosure binds to an antigen present on a target cell, thereby mediating killing of a target cell by a T lymphocyte or an NK cell genetically modified to produce the CAR. The antigen-binding domain of the CAR binds to an antigen present on the surface of a target cell.

Target cells include, but are not limited to, cancer cells. Thus, the present disclosure provides methods of killing, or inhibiting the growth of, a target cancer cell, the method involving contacting a cytotoxic immune effector cell (e.g., a cytotoxic T cell, or an NK cell) that is genetically modified to produce a subject CAR, such that the T lymphocyte or NK cell recognizes an antigen present on the surface of a target cancer cell, and mediates killing of the target cell.

The present disclosure provides a method of treating cancer in an individual having a cancer, the method comprising: i) genetically modifying T lymphocytes obtained from the individual with an expression vector comprising nucleotide sequences encoding the heterodimeric, conditionally active CAR of the present disclosure, where the antigen-binding domain of the heterodimeric, conditionally active CAR is specific for an epitope on a cancer cell in the individual, and where the genetic modification is carried out ex vivo; ii) introducing the genetically modified T lymphocytes into the individual; and iii) administering to the individual an effective amount of a dimerizing agent, wherein the dimerizing agent induces dimerization of the heterodimeric, conditionally active CAR, wherein said dimerization provides for activation of the genetically modified T lymphocytes and killing of the cancer cell, thereby treating the cancer.

Carcinomas that can be amenable to therapy by a method disclosed herein include, but are not limited to, esophageal carcinoma, hepatocellular carcinoma, basal cell carcinoma (a form of skin cancer), squamous cell carcinoma (various tissues), bladder carcinoma, including transitional cell carcinoma (a malignant neoplasm of the bladder), bronchogenic carcinoma, colon carcinoma, colorectal carcinoma, gastric carcinoma, lung carcinoma, including small cell carcinoma and non-small cell carcinoma of the lung, adrenocortical carcinoma, thyroid carcinoma, pancreatic carcinoma, breast carcinoma, ovarian carcinoma, prostate carcinoma, adenocarcinoma, sweat gland carcinoma, sebaceous gland carcinoma, papillary carcinoma, papillary adenocarcinoma, cystadenocarcinoma, medullary carcinoma, renal cell carcinoma, ductal carcinoma in situ or bile duct carcinoma, choriocarcinoma, seminoma, embryonal carcinoma, Wilm's tumor, cervical carcinoma, uterine carcinoma, testicular carcinoma, osteogenic carcinoma, epithelial carcinoma, and nasopharyngeal carcinoma.

Sarcomas that can be amenable to therapy by a method disclosed herein include, but are not limited to, fibrosarcoma, myxosarcoma, liposarcoma, chondrosarcoma, chordoma, osteogenic sarcoma, osteosarcoma, angiosarcoma, endotheliosarcoma, lymphangiosarcoma, lymphangioendotheliosarcoma, synovioma, mesothelioma, Ewing's sarcoma, leiomyosarcoma, rhabdomyosarcoma, and other soft tissue sarcomas.

Other solid tumors that can be amenable to therapy by a method disclosed herein include, but are not limited to, glioma, astrocytoma, medulloblastoma, craniopharyngioma, ependymoma, pinealoma, hemangioblastoma, acoustic neuroma, oligodendroglioma, menangioma, melanoma, neuroblastoma, and retinoblastoma.

Leukemias that can be amenable to therapy by a method disclosed herein include, but are not limited to, a) chronic myeloproliferative syndromes (neoplastic disorders of multipotential hematopoietic stem cells); b) acute myelogenous leukemias (neoplastic transformation of a multipotential hematopoietic stem cell or a hematopoietic cell of restricted lineage potential; c) chronic lymphocytic leukemias (CLL; clonal proliferation of immunologically immature and functionally incompetent small lymphocytes), including B-cell CLL, T-cell CLL prolymphocytic leukemia, and hairy cell leukemia; and d) acute lymphoblastic leukemias (characterized by accumulation of lymphoblasts). Lymphomas that can be treated using a subject method include, but are not limited to, B-cell lymphomas (e.g., Burkitt's lymphoma); Hodgkin's lymphoma; non-Hodgkin's lymphoma, and the like.

Other cancers that can be amenable to treatment according to the methods disclosed herein include atypical meningioma (brain), islet cell carcinoma (pancreas), medullary carcinoma (thyroid), mesenchymoma (intestine), hepatocellular carcinoma (liver), hepatoblastoma (liver), clear cell carcinoma (kidney), and neurofibroma mediastinum.

Immunomodulatory Methods

A subject method can also be used to treat inflammatory conditions and autoimmune disease. A subject CAR is expressed in a T-helper cell or a Tregs for use in an immunomodulatory method. Immunomodulatory methods include, e.g., enhancing an immune response in a mammalian subject toward a pathogen; enhancing an immune response in a subject who is immunocompromised; reducing an inflammatory response; reducing an immune response in a mammalian subject to an autoantigen, e.g., to treat an autoimmune disease; and reducing an immune response in a mammalian subject to a transplanted organ or tissue, to reduce organ or tissue rejection.

Where the method involves reducing an immune response to an autoantigen, the antigen used to activate the CAR is an autoantigen. Where the method involves reducing an immune response to a transplanted organ or tissue, the antigen used to activate the CAR is an antigen specific to the transplanted organ.

Formulations, Dosages, and Routes of Administration

As discussed above, a treatment method of the present disclosure involves administration to an individual in need thereof of an effective amount of a dimerizer agent, and may also involve administration of an antigen.

An “effective amount” of a dimerizer agent is in some cases an amount that, when administered in one or more doses to an individual in need thereof, increases the level of cytotoxic activity of a T lymphocyte expressing a subject CAR by at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 40%, at least about 50%, at least about 75%, at least about 2-fold, at least about 2.5-fold, at least about 5-fold, at least about 10-fold, or more than 10-fold, compared to the cytotoxic activity of the T lymphocyte in the absence of the dimerizing agent.

An “effective amount” of a dimerizer agent is in some cases an amount that, when administered in one or more doses to an individual in need thereof, increases the level of cytotoxic activity of an NK cell expressing a subject CAR by at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 40%, at least about 50%, at least about 75%, at least about 2-fold, at least about 2.5-fold, at least about 5-fold, at least about 10-fold, or more than 10-fold, compared to the cytotoxic activity of the NK cell in the absence of the dimerizing agent.

An “effective amount” of a dimerizer agent is in some cases an amount that, when administered in one or more doses to an individual in need thereof, reduces the number of cancer cells in the individual and/or reduces tumor mass in the individual, by at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 40%, at least about 50%, at least about 75%, or more than 75%, compared to the number of cancer cells and/or tumor mass in the absence of the dimerizing agent.

In some embodiments, an effective amount of a dimerizer is an amount that, when administered alone (e.g., in monotherapy) or in combination (e.g., in combination therapy) with one or more additional therapeutic agents, in one or more doses, is effective to reduce one or more of tumor growth rate, cancer cell number, and tumor mass, by at least about 5%, at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, or more, compared to the tumor growth rate, cancer cell number, or tumor mass in the absence of treatment with the dimerizer.

Formulations

In the subject methods, a dimerizer can be administered to the host using any convenient means capable of resulting in the desired therapeutic effect or diagnostic effect. Thus, the dimerizer can be incorporated into a variety of formulations for therapeutic administration. More particularly, a dimerizer can be formulated into pharmaceutical compositions by combination with appropriate, pharmaceutically acceptable carriers or diluents, and may be formulated into preparations in solid, semi-solid, liquid or gaseous forms, such as tablets, capsules, powders, granules, ointments, solutions, suppositories, injections, inhalants and aerosols.

In pharmaceutical dosage forms, a dimerizer can be administered in the form of their pharmaceutically acceptable salts, or they may also be used alone or in appropriate association, as well as in combination, with other pharmaceutically active compounds. The following methods and excipients are merely exemplary and are in no way limiting.

Suitable excipient vehicles are, for example, water, saline, dextrose, glycerol, ethanol, or the like, and combinations thereof. In addition, if desired, the vehicle may contain minor amounts of auxiliary substances such as wetting or emulsifying agents or pH buffering agents. Actual methods of preparing such dosage forms are known, or will be apparent, to those skilled in the art. See, e.g., Remington's Pharmaceutical Sciences, Mack Publishing Company, Easton, Pa., 17th edition, 1985. The composition or formulation to be administered will, in any event, contain a quantity of a dimerizer adequate to achieve the desired state in the subject being treated.

The pharmaceutically acceptable excipients, such as vehicles, adjuvants, carriers or diluents, are readily available to the public. Moreover, pharmaceutically acceptable auxiliary substances, such as pH adjusting and buffering agents, tonicity adjusting agents, stabilizers, wetting agents and the like, are readily available to the public.

For oral preparations, a dimerizer can be used alone or in combination with appropriate additives to make tablets, powders, granules or capsules, for example, with conventional additives, such as lactose, mannitol, corn starch or potato starch; with binders, such as crystalline cellulose, cellulose derivatives, acacia, corn starch or gelatins; with disintegrators, such as corn starch, potato starch or sodium carboxymethylcellulose; with lubricants, such as talc or magnesium stearate; and if desired, with diluents, buffering agents, moistening agents, preservatives and flavoring agents.

A dimerizer can be formulated into preparations for injection by dissolving, suspending or emulsifying them in an aqueous or nonaqueous solvent, such as vegetable or other similar oils, synthetic aliphatic acid glycerides, esters of higher aliphatic acids or propylene glycol; and if desired, with conventional additives such as solubilizers, isotonic agents, suspending agents, emulsifying agents, stabilizers and preservatives.

Pharmaceutical compositions comprising a dimerizer are prepared by mixing the dimerizer having the desired degree of purity with optional physiologically acceptable carriers, excipients, stabilizers, surfactants, buffers and/or tonicity agents. Acceptable carriers, excipients and/or stabilizers are nontoxic to recipients at the dosages and concentrations employed, and include buffers such as phosphate, citrate, and other organic acids; antioxidants including ascorbic acid, glutathione, cysteine, methionine and citric acid; preservatives (such as ethanol, benzyl alcohol, phenol, m-cresol, p-chlor-m-cresol, methyl or propyl parabens, benzalkonium chloride, or combinations thereof); amino acids such as arginine, glycine, ornithine, lysine, histidine, glutamic acid, aspartic acid, isoleucine, leucine, alanine, phenylalanine, tyrosine, tryptophan, methionine, serine, proline and combinations thereof; monosaccharides, disaccharides and other carbohydrates; low molecular weight (less than about 10 residues) polypeptides; proteins, such as gelatin or serum albumin; chelating agents such as EDTA; sugars such as trehalose, sucrose, lactose, glucose, mannose, maltose, galactose, fructose, sorbose, raffinose, glucosamine, N-methylglucosamine, galactosamine, and neuraminic acid; and/or non-ionic surfactants such as Tween, Brij Pluronics, Triton-X, or polyethylene glycol (PEG).

The pharmaceutical composition may be in a liquid form, a lyophilized form or a liquid form reconstituted from a lyophilized form, wherein the lyophilized preparation is to be reconstituted with a sterile solution prior to administration. The standard procedure for reconstituting a lyophilized composition is to add back a volume of pure water (typically equivalent to the volume removed during lyophilization); however solutions comprising antibacterial agents may be used for the production of pharmaceutical compositions for parenteral administration; see also Chen (1992) Drug Dev Ind Pharm 18, 1311-54.

The term “unit dosage form,” as used herein, refers to physically discrete units suitable as unitary dosages for human and animal subjects, each unit containing a predetermined quantity a dimerizer calculated in an amount sufficient to produce the desired effect in association with a pharmaceutically acceptable diluent, carrier or vehicle. The specifications for a given dimerizer may depend on the particular dimerizer employed and the effect to be achieved, and the pharmacodynamics associated with each dimerizer in the host.

In some embodiments, a dimerizer is formulated in a controlled release formulation. Sustained-release preparations may be prepared using methods well known in the art. Suitable examples of sustained-release preparations include semipermeable matrices of solid hydrophobic polymers containing the dimerizer in which the matrices are in the form of shaped articles, e.g. films or microcapsules. Examples of sustained-release matrices include polyesters, copolymers of L-glutamic acid and ethyl-L-glutamate, non-degradable ethylene-vinyl acetate, hydrogels, polylactides, degradable lactic acid-glycolic acid copolymers and poly-D-(−)-3-hydroxybutyric acid. Possible loss of biological activity may be prevented by using appropriate additives, by controlling moisture content and by developing specific polymer matrix compositions.

Dosages

A suitable dosage can be determined by an attending physician or other qualified medical personnel, based on various clinical factors. As is well known in the medical arts, dosages for any one patient depend upon many factors, including the patient's size, body surface area, age, the particular dimerizer to be administered, sex of the patient, time, and route of administration, general health, and other drugs being administered concurrently. A dimerizer may be administered in amounts between 1 ng/kg body weight and 20 mg/kg body weight per dose, e.g. between 0.1 mg/kg body weight to 10 mg/kg body weight, e.g. between 0.5 mg/kg body weight to 5 mg/kg body weight; however, doses below or above this exemplary range are envisioned, especially considering the aforementioned factors. If the regimen is a continuous infusion, it can also be in the range of 1 μg to 10 mg per kilogram of body weight per minute.

Those of skill will readily appreciate that dose levels can vary as a function of the specific dimerizer, the severity of the symptoms and the susceptibility of the subject to side effects. Preferred dosages for a given compound are readily determinable by those of skill in the art by a variety of means.

Routes of Administration

A dimerizer is administered to an individual using any available method and route suitable for drug delivery, including in vivo and ex vivo methods, as well as systemic and localized routes of administration.

Conventional and pharmaceutically acceptable routes of administration include intratumoral, peritumoral, intramuscular, intratracheal, intracranial, subcutaneous, intradermal, topical application, intravenous, intraarterial, rectal, nasal, oral, and other enteral and parenteral routes of administration. Routes of administration may be combined, if desired, or adjusted depending upon the dimerizer and/or the desired effect. A dimerizer can be administered in a single dose or in multiple doses. In some embodiments, a dimerizer is administered orally. In some embodiments, a dimerizer is administered via an inhalational route. In some embodiments, a dimerizer is administered intranasally. In some embodiments, a dimerizer is administered locally. In some embodiments, a dimerizer is administered intratumorally. In some embodiments, a dimerizer is administered peritumorally. In some embodiments, a dimerizer is administered intracranially. In some embodiments, a dimerizer is administered intravenously.

The agent can be administered to a host using any available conventional methods and routes suitable for delivery of conventional drugs, including systemic or localized routes. In general, routes of administration contemplated by the invention include, but are not necessarily limited to, enteral, parenteral, or inhalational routes.

Parenteral routes of administration other than inhalation administration include, but are not necessarily limited to, topical, transdermal, subcutaneous, intramuscular, intraorbital, intracapsular, intraspinal, intrasternal, intratumoral, peritumoral, and intravenous routes, i.e., any route of administration other than through the alimentary canal. Parenteral administration can be carried to effect systemic or local delivery of a dimerizer. Where systemic delivery is desired, administration typically involves invasive or systemically absorbed topical or mucosal administration of pharmaceutical preparations.

A dimerizer can also be delivered to the subject by enteral administration. Enteral routes of administration include, but are not necessarily limited to, oral and rectal (e.g., using a suppository) delivery.

By treatment is meant at least an amelioration of the symptoms associated with the pathological condition afflicting the host, where amelioration is used in a broad sense to refer to at least a reduction in the magnitude of a parameter, e.g. symptom, associated with the pathological condition being treated, such as cancer. As such, treatment also includes situations where the pathological condition, or at least symptoms associated therewith, are completely inhibited, e.g. prevented from happening, or stopped, e.g. terminated, such that the host no longer suffers from the pathological condition, or at least the symptoms that characterize the pathological condition.

In some embodiments, a dimerizer is administered by injection and/or delivery, e.g., to a site in a brain artery or directly into brain tissue. A dimerizer can also be administered directly to a target site e.g., by direct injection, by implantation of a drug delivery device such as an osmotic pump or slow release particle, by biolistic delivery to the target site, etc.

Combination Therapy

In some embodiments, a dimerizer is administered as an adjuvant therapy to a standard cancer therapy. Standard cancer therapies include surgery (e.g., surgical removal of cancerous tissue), radiation therapy, bone marrow transplantation, chemotherapeutic treatment, antibody treatment, biological response modifier treatment, and certain combinations of the foregoing.

Radiation therapy includes, but is not limited to, x-rays or gamma rays that are delivered from either an externally applied source such as a beam, or by implantation of small radioactive sources.

Suitable antibodies for use in cancer treatment include, but are not limited to, naked antibodies, e.g., trastuzumab (Herceptin) , bevacizumab (Avastin™), cetuximab (Erbitux™), panitumumab (Vectibix™), Ipilimumab (Yervoy™), rituximab (Rituxan), alemtuzumab (Lemtrada™), Ofatumumab (Arzerra™), Oregovomab (OvaRex™) Lambrolizumab (MK-3475), pertuzumab (Perjeta™), ranibizumab (Lucentis™) etc., and conjugated antibodies, e.g., gemtuzumab ozogamicin (Mylortarg™), Brentuximab vedotin (Adcetris™), ⁹⁰Y-labelled ibritumomab tiuxetan (Zevalin™), ¹³¹I-labelled tositumoma (Bexxar™), etc. Suitable antibodies for use in cancer treatment include, but are not limited to, antibodies raised against tumor-associated antigens. Such antigens include, but are not limited to, CD20, CD30, CD33, CD52, EpCAM, CEA, gpA33, Mucins, TAG-72, CAIX, PSMA, Folate-binding protein, Gangliosides (e.g., GD2, GD3, GM2, etc.), Le^(y) , VEGF, VEGFR, Integrin alpha-V-beta-3, Integrin alpha-5-beta-1, EGFR, ERBB2, ERBB3, MET, IGF1R, EPHA3, TRAILR1, TRAILR2, RANKL, FAP, Tenascin, etc.

Biological response modifiers suitable for use in connection with the methods of the present disclosure include, but are not limited to, (1) inhibitors of tyrosine kinase (RTK) activity; (2) inhibitors of serine/threonine kinase activity; (3) tumor-associated antigen antagonists, such as antibodies that bind specifically to a tumor antigen; (4) apoptosis receptor agonists; (5) interleukin-2; (6) interferon-α; (7) interferon -γ; (8) colony-stimulating factors; (9) inhibitors of angiogenesis; and (10) antagonists of tumor necrosis factor.

Chemotherapeutic agents are non-peptidic (i.e., non-proteinaceous) compounds that reduce proliferation of cancer cells, and encompass cytotoxic agents and cytostatic agents. Non-limiting examples of chemotherapeutic agents include alkylating agents, nitrosoureas, antimetabolites, antitumor antibiotics, plant (vinca) alkaloids, and steroid hormones.

Agents that act to reduce cellular proliferation are known in the art and widely used.

Such agents include alkylating agents, such as nitrogen mustards, nitrosoureas, ethylenimine derivatives, alkyl sulfonates, and triazenes, including, but not limited to, mechlorethamine, cyclophosphamide (Cytoxan™), melphalan (L-sarcolysin), carmustine (BCNU), lomustine (CCNU), semustine (methyl-CCNU), streptozocin, chlorozotocin, uracil mustard, chlormethine, ifosfamide, chlorambucil, pipobroman, triethylenemelamine, triethylenethiophosphoramine, busulfan, dacarbazine, and temozolomide.

Antimetabolite agents include folic acid analogs, pyrimidine analogs, purine analogs, and adenosine deaminase inhibitors, including, but not limited to, cytarabine (CYTOSAR-U), cytosine arabinoside, fluorouracil (5-FU), floxuridine (FudR), 6-thioguanine, 6-mercaptopurine (6-MP), pentostatin, 5-fluorouracil (5-FU), methotrexate, 10-propargyl-5,8-dideazafolate (PDDF, CB3717), 5,8-dideazatetrahydrofolic acid (DDATHF), leucovorin, fludarabine phosphate, pentostatine, and gemcitabine.

Suitable natural products and their derivatives, (e.g., vinca alkaloids, antitumor antibiotics, enzymes, lymphokines, and epipodophyllotoxins), include, but are not limited to, Ara-C, paclitaxel (Taxol®), docetaxel (Taxotere®), deoxycoformycin, mitomycin-C, L-asparaginase, azathioprine; brequinar; alkaloids, e.g. vincristine, vinblastine, vinorelbine, vindesine, etc.; podophyllotoxins, e.g. etoposide, teniposide, etc.; antibiotics, e.g. anthracycline, daunorubicin hydrochloride (daunomycin, rubidomycin, cerubidine), idarubicin, doxorubicin, epirubicin and morpholino derivatives, etc.; phenoxizone biscyclopeptides, e.g. dactinomycin; basic glycopeptides, e.g. bleomycin; anthraquinone glycosides, e.g. plicamycin (mithramycin); anthracenediones, e.g. mitoxantrone; azirinopyrrolo indolediones, e.g. mitomycin; macrocyclic immunosuppressants, e.g. cyclosporine, FK-506 (tacrolimus, prograf), rapamycin, etc.; and the like.

Other anti-proliferative cytotoxic agents are navelbene, CPT-11, anastrazole, letrazole, capecitabine, reloxafine, cyclophosphamide, ifosamide, and droloxafine.

Microtubule affecting agents that have antiproliferative activity are also suitable for use and include, but are not limited to, allocolchicine (NSC 406042), Halichondrin B (NSC 609395), colchicine (NSC 757), colchicine derivatives (e.g., NSC 33410), dolstatin 10 (NSC 376128), maytansine (NSC 153858), rhizoxin (NSC 332598), paclitaxel (Taxol®), Taxol® derivatives, docetaxel (Taxotere®), thiocolchicine (NSC 361792), trityl cysterin, vinblastine sulfate, vincristine sulfate, natural and synthetic epothilones including but not limited to, eopthilone A, epothilone B, discodermolide; estramustine, nocodazole, and the like.

Hormone modulators and steroids (including synthetic analogs) that are suitable for use include, but are not limited to, adrenocorticosteroids, e.g. prednisone, dexamethasone, etc.; estrogens and pregestins, e.g. hydroxyprogesterone caproate, medroxyprogesterone acetate, megestrol acetate, estradiol, clomiphene, tamoxifen; etc.; and adrenocortical suppressants, e.g. aminoglutethimide; 17α-ethinylestradiol; diethylstilbestrol, testosterone, fluoxymesterone, dromostanolone propionate, testolactone, methylprednisolone, methyl-testosterone, prednisolone, triamcinolone, chlorotrianisene, hydroxyprogesterone, aminoglutethimide, estramustine, medroxyprogesterone acetate, leuprolide, Flutamide (Drogenil), Toremifene (Fareston), and Zoladex®. Estrogens stimulate proliferation and differentiation, therefore compounds that bind to the estrogen receptor are used to block this activity. Corticosteroids may inhibit T cell proliferation.

Other chemotherapeutic agents include metal complexes, e.g. cisplatin (cis-DDP), carboplatin, etc.; ureas, e.g. hydroxyurea; and hydrazines, e.g. N-methylhydrazine; epidophyllotoxin; a topoisomerase inhibitor; procarbazine; mitoxantrone; leucovorin; tegafur; etc. Other anti-proliferative agents of interest include immunosuppressants, e.g. mycophenolic acid, thalidomide, desoxyspergualin, azasporine, leflunomide, mizoribine, azaspirane (SKF 105685); Iressa® (ZD 1839, 4-(3-chloro-4-fluorophenylamino)-7-methoxy-6-(3-(4-morpholinyl)propoxy)quinazoline); etc.

“Taxanes” include paclitaxel, as well as any active taxane derivative or pro-drug. “Paclitaxel” (which should be understood herein to include analogues, formulations, and derivatives such as, for example, docetaxel, TAXOL™, TAXOTERE™ (a formulation of docetaxel), 10-desacetyl analogs of paclitaxel and 3′N-desbenzoyl-3′N-t-butoxycarbonyl analogs of paclitaxel) may be readily prepared utilizing techniques known to those skilled in the art (see also WO 94/07882, WO 94/07881, WO 94/07880, WO 94/07876, WO 93/23555, WO 93/10076; U.S. Pat. Nos. 5,294,637; 5,283,253; 5,279,949; 5,274,137; 5,202,448; 5,200,534; 5,229,529; and EP 590,267), or obtained from a variety of commercial sources, including for example, Sigma Chemical Co., St. Louis, Mo. (T7402 from Taxus brevifolia; or T-1912 from Taxus yannanensis).

Paclitaxel should be understood to refer to not only the common chemically available form of paclitaxel, but analogs and derivatives (e.g., Taxotere™ docetaxel, as noted above) and paclitaxel conjugates (e.g., paclitaxel-PEG, paclitaxel-dextran, or paclitaxel-xylose).

Also included within the term “taxane” are a variety of known derivatives, including both hydrophilic derivatives, and hydrophobic derivatives. Taxane derivatives include, but not limited to, galactose and mannose derivatives described in International Patent Application No. WO 99/18113; piperazino and other derivatives described in WO 99/14209; taxane derivatives described in WO 99/09021, WO 98/22451, and U.S. Pat. No. 5,869,680; 6-thio derivatives described in WO 98/28288; sulfenamide derivatives described in U.S. Pat. No. 5,821,263; and taxol derivative described in U.S. Pat. No. 5,415,869. It further includes prodrugs of paclitaxel including, but not limited to, those described in WO 98/58927; WO 98/13059; and U.S. Pat. No. 5,824,701.

Subjects Suitable for Treatment

A variety of subjects are suitable for treatment with a subject method of treating cancer. Suitable subjects include any individual, e.g., a human or non-human animal who has cancer, who has been diagnosed with cancer, who is at risk for developing cancer, who has had cancer and is at risk for recurrence of the cancer, who has been treated with an agent other than a dimerizer for the cancer and failed to respond to such treatment, or who has been treated with an agent other than a dimerizer for the cancer but relapsed after initial response to such treatment.

Subjects suitable for treatment with a subject immunomodulatory method include individuals who have an autoimmune disorder; individuals who are organ or tissue transplant recipients; and the like; individuals who are immunocompromised; and individuals who are infected with a pathogen.

EXAMPLES

The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how to make and use the present invention, and are not intended to limit the scope of what the inventors regard as their invention nor are they intended to represent that the experiments below are all or the only experiments performed. Efforts have been made to ensure accuracy with respect to numbers used (e.g. amounts, temperature, etc.) but some experimental errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, molecular weight is weight average molecular weight, temperature is in degrees Celsius, and pressure is at or near atmospheric. Standard abbreviations may be used, e.g., bp, base pair(s); kb, kilobase(s); pl, picoliter(s); s or sec, second(s); min, minute(s); h or hr, hour(s); aa, amino acid(s); kb, kilobase(s); bp, base pair(s); nt, nucleotide(s); i.m., intramuscular(ly); i.p., intraperitoneal(ly); s.c., subcutaneous(ly); i.v., intravenous(ly); and the like.

Example 1 Generation of CAR

Materials and Methods

The anti-human CD19 scFv was selected as the antigen recognition domain in CARs throughout the design optimization process. FIGS. 18A and 18B summarize the molecular structure of each CAR consisting of two numerically identified polypeptides. All membrane-anchored polypeptides are di-sulfide bonded homo-dimers. The membrane-anchored polypeptides are depicted as monomers for graphical simplicity.

Generation of CAR Constructs

Sequence encoding the anti-human CD19 scFv was cloned from a construct. The human 4-1BB co-stimulation and CD3 zeta ITAM signaling chains were cloned from cDNAs supplied by Open Biosystems. FKBP- and FRB-encoding sequences were cloned from plasmids supplied by Addgene.

Standard molecular cloning techniques (polymerase chain reaction (PCR), restriction digestion, ligation, etc.) were applied to generate lentiviral expression plasmids.

Effector and Target Cell Culturing Conditions

Human primary CD8+ T cells were isolated from anonymous donor's blood after apheresis (Trima residuals from Blood Centers of the Pacific, San Francisco, Calif.) by negative selection using RosetteSep Human CD8+ T Cell Enrichment Cocktail (STEMCELL Technologies #15063) as approved by University Institutional Review Board. Cells were cultured in human T cell medium, consisting of X-VIVO15 (Lonza #04-418Q), 5% human AB serum (Valley Biomedical Inc., #HP1022), 10mM N-acetyl L-Cysteine (Sigma-Aldrich #A9165) and 100 IU/mL recombinant human IL-2 (NCl/BRB Preclinical Repository). A Jurkat cell line expressing the Green Fluorescent Protein (GFP) upon NFAT activation was maintained in RPMI-1640 medium supplemented with 10% fetal bovine serum (FBS), penicillin and streptomycin. K562 target cells from U. Penn were cultured in IMDM supplemented with 10% FBS.

Effector and Target Cell Engineering with Lentivirus

Pantropic VSV-G pseudotyped lentivirus was produced from Lenti-X 293T cells (Clontech Laboratories #632180) co-transfected with a pHR'SIN:CSW transgene expression vector, viral packaging plasmids pCMVdR8.91 and pMD2.G using Lipofectamine LTX (Life Technologies #15338). Infection medium supernatant was collected 48 hours after transfection and used directly for transduction.

Twenty four hours prior to viral transduction, primary human T cells were activated using the human T-Activator CD3/CD28 Dynabeads (Life Technologies #111-31D) at a 1:3 cell:bead ratio. Jurkat and K562 cells were split 1˜2 days in advance to ensure that cultures would be in log phase at the time of transduction. Transduced Jurkat and K562 cells were cultured for at least 7 days before experiments were conducted. Primary T cells were maintained at ˜10̂6/mL in human T cell medium for about two weeks until cells returned to a resting state. Expression levels of CARs encoded in the lentiviral constructs were quantified by detecting either fluorophore-conjugated antibodies or fluorescent reporter proteins using a flow cytometer.

Quantitation of IL-2 Production and NFAT Activity

Jurkat CD4+ T cells expressing CARs were mixed with cognate or non-cognate K562 target cells from U. Penn at a 1:2 effector:target ratio. The rapalog A/C Heterodimerizer (Clontech Laboratories #635055) were serially diluted in medium and added to reaction mixtures. After 20˜24 hours of incubation, medium supernatants were collected and analyzed with BD OptEIA Human IL-2 ELISA Set (BD Biosciences #555190). Flow cytometry was performed to quantify NFAT-dependent GFP reporter expression in Jurkat cells as a separate indicator for CAR activity.

Flow Cytometry-Based Re-Directed Cytotoxicity Assay

The cognate and non-cognate K562 target cells were engineered to express distinct fluorescent proteins so that both cell types in a mixture could be simultaneously quantified by flow cytometry. The target cell types were mixed at a 1:1 ratio and co-incubated with human primary CD8+ effector T cells at a 5:2 effector:target ratio. 100 IU/mL human IL-2 and varying amounts of the rapalog (Clontech Laboratories #635055) were added to reaction mixtures. After 24 hours of incubation, samples were centrifuged at 400 g for 5 minutes. Pelleted cells were resuspended in wash buffer (PBS+0.5% BSA+0.1% sodium azide) and fixed with an equal volume of BD Cytofix (BD cat #554655) prior to flow cytometry. Ratios of the surviving cognate target cells to non-cognate target cells were calculated for each sample to enumerate re-directed cytotoxic activities of the effector cells.

Results

IL-2 production elicited by the various CAR constructs was assessed. The data are presented in FIG. 12.

FIG. 12. IL-2 production triggered by five On-switch CAR variants. Effector=human CD4+ Jurkat T cells engineered with CARs. Target=K562 cell lines with or without the cognate CD19 antigen. Amounts of secreted IL-2 by effector cells were quantified by enzyme-linked immunosorbent assay (ELISA).

FIG. 13. IL-2 production by control Jurkat lines in the same experiment as that described in FIG. 12. Construct “125” encodes a conventional control currently used in clinical trials.

FIG. 14. Comparison between “122+206” and “197+206” in a separate experiment under conditions identical to those described in FIG. 12.

FIG. 15 demonstrates pharmacologically titratable cytoxicity conferred by the On-switch CAR “197+206” In the presence of the small molecule rapalog, the CAR effectively mediates re-directed cytotoxicity towards cognate target cells. At high dosages of rapalog, this On-switch CAR can signal as strongly as the “125” conventional CAR. Effector=human primary CD8+ T cells engineered with CARs or a control vector. Target=fluorescent derivatives of K562 cell lines expressing either the cognate human CD19 antigen or the non-cognate human mesothelin antigen.

FIG. 16 depicts data for CARs constructed with the cytoplasmic tyrosine kinase Zap70 from the T cell receptor pathway as the intracellular signaling domain.

FIG. 16 shows data from Jurkat cells engineered with several variants of On-switch CARs. The engineered Jurkat cells were co-incubated with K562 target cells with or without the cognate antigen (CD19) and the indicated concentrations of rapalog. As a CAR component, the Zap70 kinase (first and second structures from left featuring “199”) was as effective as the ITAM (third structure from left featuring “168”) in activating NFAT function. Addition of the 4-1BB signaling domain increased surface expression of the antigen recognition portion of the receptor and led to stronger signaling by “197+199”. A non-signaling CAR (far-right) was included as a negative control.

Example 2 CARs Targeting Mesothelin

Materials and Methods

A number of chimeric antigen receptor constructs were made and tested. The constructs shown here encode three different anti-human mesothelin scFv as the antigen recognition domains. FIGS. 19A, 19B, and 19C summarize the molecular structure of each anti-human mesothelin CAR, with each CAR comprising two polypeptides. The intercellular portion of each anti-human mesothelin CAR comprises two 4-1BB co-stimulatory domains, an FKBP and FRB dimerizer-binding pair, and an ITAM intracellular signaling domain. The three different antigen recognition domains shown here are anti-mesothelin HN1 scFv, SS1 scFv, and m912 scFv. All membrane-anchored polypeptides are di-sulfide bonded homo-dimers.

Generation of CAR Constructs

Sequences encoding the anti-mesothelin were cloned from constructs or synthesized via gene assembly by PCR. The human 4-1BB co-stimulation and CD3 zeta ITAM signaling chains were cloned from cDNAs supplied by Open Biosystems. HN1 scFv-, SS1 scFv-, and m912 scFv-encoding sequences were synthesized by PCR and, in some cases, codon optimized. FKBP- and FRB-encoding sequences were cloned from Addgene plasmids.

Standard molecular cloning techniques (polymerase chain reaction (PCR), restriction digestion, ligation, etc.) were applied to generate lentiviral expression plasmids.

Effector and Target Cell Culturing Conditions

A Jurkat cell line expressing GFP upon NFAT activation was maintained in RPMI-1640 medium supplemented with 10% FBS, penicillin and streptomycin. K562 target cells were cultured in IMDM supplemented with 10% fetal bovine serum (FBS).

Effector and Target Cell Engineering with Lentivirus

Pantropic VSV-G pseudotyped lentivirus was produced from Lenti-X 293T cells (Clontech Laboratories #632180) co-transfected with a pHR'SIN:CSW transgene expression vector, viral packaging plasmids pCMVdR8.91 and pMD2.G using Lipofectamine LTX (Life Technologies #15338). Infection medium supernatant was collected 48 hours after transfection and used directly for transduction.

Jurkat and K562 cells were split 1˜2 days in advance to ensure that cultures would be in log phase at the time of transduction. Transduced Jurkat and K562 cells were cultured for at least 7 days before experiments were conducted. Expression levels of CARs encoded in the lentiviral constructs were quantified by detecting either fluorophore-conjugated antibodies or fluorescent reporter proteins using a flow cytometer.

Quantitation of IL-2 Production

Jurkat CD4+ T cells expressing CARs were mixed with cognate or non-cognate K562 target cells at a 1:2 effector:target ratio. The rapalog A/C Heterodimerizer (Clontech Laboratories #635055) were serially diluted in medium and added to reaction mixtures. After 20˜24 hours of incubation, medium supernatants were collected and analyzed with BD OptEIA Human IL-2 ELISA Set (BD Biosciences #555190).

Results

IL-2 production elicited by the anti-mesothelin CAR constructs was assessed. The data are presented in FIG. 19D-F.

FIG. 19. IL-2 production triggered by HN1 scFv (FIG. 19D), SS1 scFv (FIG. 19E), and m912 scFv (FIG. 19F) On-switch CAR variants. IL-2 production by a conventional CAR (FIG. 19G, construct #358) was measured and included for comparison to On-switch CARs (FIG. 19D). Effector=human CD4+ Jurkat T cells engineered with CARs. Target=K562 cell lines with or without the cognate mesothelin antigen. Amounts of secreted IL-2 by effector cells were quantified by enzyme-linked immunosorbent assay (ELISA).

Example 3 Gibberellic Acid as a Dimerizer of On-Switch CARs

Materials and Methods

FIG. 20A summarizes the molecular structure of the subject gibberellic acid dimerizer CAR. The antigen binding portion comprises the anti-human CD19 scFv. The intracellular portion comprises two 4-1BB co-stimulatory domains, a GID1 and GAI dimerizer-binding pair, and an ITAM intracellular signaling domain. All membrane-anchored polypeptides are di-sulfide bonded homo-dimers.

Generation of CAR Constructs

Sequences encoding the gibberellic acid dimerizer CAR were cloned from constructs. The anti-CD 19 scFv was cloned from a plasmid. The human 4-1BB co-stimulation and CD3 zeta ITAM signaling chains were cloned from cDNAs supplied by Open Biosystems. GID1- and GAI-encoding sequences were cloned from Addgene plasmids. Standard molecular cloning techniques (polymerase chain reaction (PCR), restriction digestion, ligation, etc.) were applied to generate lentiviral expression plasmids.

Effector and Target Cell Culturing Conditions

A Jurkat cell line expressing GFP upon NFAT activation was maintained in RPMI-1640 medium supplemented with 10% FBS, penicillin and streptomycin. K562 target cells were cultured in IMDM supplemented with 10% fetal bovine serum (FBS).

Effector and Target Cell Engineering with Lentivirus

Pantropic VSV-G pseudotyped lentivirus was produced from Lenti-X 293T cells (Clontech Laboratories #632180) co-transfected with a pHR'SIN:CSW transgene expression vector, viral packaging plasmids pCMVdR8.91 and pMD2.G using Lipofectamine LTX (Life Technologies #15338). Infection medium supernatant was collected 48 hours after transfection and used directly for transduction.

Jurkat and K562 cells were split 1˜2 days in advance to ensure that cultures would be in log phase at the time of transduction. Transduced Jurkat and K562 cells were cultured for at least 7 days before experiments were conducted. Expression levels of CARs encoded in the lentiviral constructs were quantified by detecting either fluorophore-conjugated antibodies or fluorescent reporter proteins using a flow cytometer.

Quantitation of IL-2 Production

Jurkat CD4+ T cells expressing CARs were mixed with cognate or non-cognate K562 target cells at a 1:2 effector:target ratio. The gibberellic acid-3 acetoxymethyl ester (gibberrelic acid-3 AM) pre-dissolved in ethanol (Toronto Research Chemicals #G377500) was diluted in growth medium and added to reaction mixtures. Gibberellic acid (gibberellic acid-3 AM) was used at 10 mM. After 20˜24 hours of incubation, medium supernatants were collected and analyzed with BD OptEIA Human IL-2 ELISA Set (BD Biosciences #555190).

Results

IL-2 production elicited by the gibberellic acid dimerizer CAR construct was assessed. The data are presented in FIG. 20.

FIG. 20. IL-2 production triggered by gibberellic acid dimerizer CAR variant (FIG. 20B). IL-2 production by a conventional CAR (FIG. 20C, construct “125”) was measured and included for comparison to On-switch CAR. Effector=human CD4+ Jurkat T cells engineered with CARs. Target=K562 cell lines with or without the cognate CD19 antigen. Amounts of secreted IL-2 by effector cells were quantified by enzyme-linked immunosorbent assay (ELISA).

Example 4 On-Switch CARs with Various Co-Stimulatory Domains

Materials and Methods

A number of chimeric antigen receptor constructs were made essentially as described for Example 1, except various other co-stimulatory domains were exchanged for the 4-1BB co-stimulatory domains. FIGS. 21A and 21B summarize the molecular structure of the CARs described here.

Generation of CAR Constructs

Sequences encoding the anti-human CD19 scFv were cloned from a plasmid. The human CD3 zeta ITAM signaling chain and the human co-stimulatory domains CD28 and OX-40 encoding sequences were cloned from cDNAs supplied by Open Biosystems. FKBP- and FRB-encoding sequences were cloned from plasmids from Addgene.

Standard molecular cloning techniques (polymerase chain reaction (PCR), restriction digestion, ligation, etc.) were applied to generate lentiviral expression plasmids.

Testing of CAR Constructs

Effector and target cells are cultured and transfected according to Example 1 using the on-switch CAR CD28 and OX-40 co-stimulatory domain containing constructs described (FIG. 21A-B, constructs “365+367” and “399+400”, respectively) and corresponding conventional CAR controls (FIG. 21C-D, constructs “366” and “398”, respectively). IL-2 production, NFAT activity assays, and flow cytometry-based assays can also be performed with the CD28 co-stimulatory domain containing construct and OX-40 co-stimulatory domain containing construct as described for Example 1. Alternatively, subunits of on-switch CAR CD28 and OX-40 co-stimulatory domain containing constructs can be paired with subunits of constructs from Example 1 (e.g., “197+367”, “365+206,” “197+400”, “399+206,” etc.).

Example 5 In Vivo Assessment of On-Switch CAR

An On-switch CAR can be assessed for its ability to mediate in vivo killing of a target tumor cell. In vivo tumor cell killing elicited by injection of T cells expressing the ON-switch CAR is assessed. Tumor cell lines that have been confirmed in vitro to express the cognate antigen and can be killed by CD8⁺ T cells expressing the corresponding CAR are used. Tumor cells engineered to express either the firefly or Renilla luciferase to enable bio-luminescence imaging to quantify tumor burden in vivo can be used. Tumor cells are injected into immunocompromised mice (e.g., 6˜10 week old female NOD scid gamma (NSG) mice) either subcutaneously for subcutaneous tumor models or intravenously for systemic tumor models. The method of tumor implantation and the optimal number of tumor cells to implant can be based on conditions optimal for the tumor cell line used. Tumor burden can be monitored twice a week by bio-luminescence imaging and by caliper measurement when applicable. As soon as tumor burden is detectable, 0.5˜2.5×10̂7 total T cells (1:1 CD4⁺:CD8⁺) expressing the ON-switch CAR are intravenously injected into mice to begin treatment. A dimerizing small molecule drug (e.g., rapalog) is administered intraperitoneally in a vehicle formulation. On-switch CAR-expressing T cells can be injected repeatedly during the experiment to enhance the anti-tumor effect. Interleukin-2 (IL-2) can be administered to enhance the anti-tumor effect.

While the present invention has been described with reference to the specific embodiments thereof, it should be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process, process step or steps, to the objective, spirit and scope of the present invention. All such modifications are intended to be within the scope of the claims appended hereto. 

What is claimed is:
 1. A heterodimeric, conditionally active chimeric antigen receptor (CAR) comprising: a) a first polypeptide comprising: i) a first member of a specific binding pair; ii) a first modulatory domain; iii) a first member of a dimerization pair; and iv) a transmembrane domain interposed between the first member of a specific binding pair and the first modulatory domain; and b) a second polypeptide comprising: i) a transmembrane domain; ii) a second modulatory domain; iii) a second member of the dimerization pair; and iv) an intracellular signaling domain; or comprising: a) a first polypeptide comprising: i) a first member of a specific binding pair; ii) a modulatory domain; iii) a first member of a dimerization pair; iv) a transmembrane domain interposed between the first member of a specific binding pair and the modulatory domain; and b) a second polypeptide comprising: i) a second member of the dimerization pair; and ii) an intracellular signaling domain.
 2. The heterodimeric, conditionally active CAR of claim 1, wherein the first polypeptide comprises a hinge region interposed between the first member of the specific binding pair and the transmembrane domain.
 3. The heterodimeric, conditionally active CAR of claim 1, wherein the first member of the specific binding pair is an antibody or antibody fragment, a ligand, or a receptor.
 4. The heterodimeric, conditionally active CAR of claim 2, wherein the hinge region is an immunoglobulin IgG hinge region or a hinge derived from CD8.
 5. The heterodimeric, conditionally active CAR of claim 1, wherein the first and second modulatory domains are selected from 4-1BB (CD137), CD28, ICOS, BTLA, OX-40, CD27, CD30, GITR, HVEM, DAP10, DAP12, and CD28.
 6. The heterodimeric, conditionally active CAR of claim 1, wherein the intracellular signaling domain is selected from ZAP70 and CD3-zeta.
 7. The heterodimeric, conditionally active CAR of claim 1, wherein the intracellular signaling domain comprises an immunoreceptor tyrosine-based activation motif (ITAM).
 8. The heterodimeric, conditionally active CAR of claim 1, wherein the first and second members of the dimerization pair form a homodimer in the presence of a small molecule dimerizer.
 9. The heterodimeric, conditionally active CAR of claim 1, wherein the first and second members of the dimerization pair form a heterodimer in the presence of a small molecule dimerizer.
 10. The heterodimeric, conditionally active CAR of claim 1, wherein the first and second members of the dimerization pair are selected from: a) FK506 binding protein (FKBP) and FKBP; b) FKBP and calcineurin catalytic subunit A (CnA); c) FKBP and cyclophilin; d) FKBP and FKBP-rapamycin associated protein (FRB); e) gyrase B (GyrB) and GyrB; f) dihydrofolate reductase (DHFR) and DHFR; g) DmrB and DmrB; h) PYL and ABI; i) Cry2 and CIP; j) GAI and GID1.
 11. The heterodimeric, conditionally active CAR of claim 1, wherein: i) the first and second modulatory domains are derived from 4-1BB; ii) the first and second members of the dimerization pair are FKBP and FRB; and ii) the signaling domain comprises an ITAM.
 12. The heterodimeric, conditionally active CAR of claim 1, wherein the first member of the specific binding pair is a single-chain Fv.
 13. The heterodimeric, conditionally active CAR of claim 1, wherein the first member of the specific binding pair binds an epitope present on a cell, on a solid surface, or a lipid bilayer.
 14. The heterodimeric, conditionally active CAR of claim 13, wherein the cell is a cancer cell.
 15. A mammalian cell genetically modified to produce the heterodimeric, conditionally active CAR of claim
 1. 16. The cell of claim 15, wherein the cell is a stem cell, a progenitor cell, or a cell derived from a stem cell or a progenitor cell.
 17. The cell of claim 15, wherein the cell is a T lymphocyte or an NK cell.
 18. A nucleic acid comprising nucleotide sequences encoding the heterodimeric, conditionally active CAR of claim
 1. 19. The nucleic acid of claim 18, wherein the nucleotide sequences are operably linked to a T lymphocyte-specific promoter or an NK cell-specific promoter.
 20. The nucleic acid of claim 18, wherein the nucleic acid is in vitro transcribed RNA.
 21. A recombinant expression vector comprising the nucleic acid of claim
 18. 22. A method of activating a T lymphocyte, the method comprising contacting the T lymphocyte with a dimerizing agent and a second member of a specific binding pair, wherein the T lymphocyte is genetically modified to produce a heterodimeric, conditionally active CAR of claim 1, and wherein, in the presence of the dimerizing agent and the second member of a specific binding pair, the heterodimeric, conditionally active CAR dimerizes and activates the T lymphocyte, thereby producing an activated T lymphocyte.
 23. The method of claim 22, wherein the second member of a specific binding pair is an antigen.
 24. The method of claim 22, wherein said contacting occurs in vivo.
 25. The method of claim 22, wherein the activated T lymphocyte mediates killing of a target cell.
 26. The method of claim 22, wherein the activated T lymphocyte produces IL-2 and/or IFN-γ.
 27. The method of claim 25, wherein the target cell is a cancer cell.
 28. The method of claim 22, wherein the first member of the specific binding pair of the heterodimeric, conditionally active CAR is an antibody specific for an epitope on a cancer cell.
 29. A method of making the cell of claim 15, the method comprising genetically modifying a mammalian cell with an expression vector comprising nucleotide sequences encoding the heterodimeric, conditionally active CAR of claim 1, or genetically modifying a mammalian cell with an RNA comprising nucleotide sequences encoding the heterodimeric, conditionally active CAR of claim
 1. 30. The method of claim 29, wherein said genetic modification is carried out ex vivo.
 31. The method of claim 29, wherein the cell is a T lymphocyte, a stem cell, an NK cell, a progenitor cell, a cell derived from a stem cell, or a cell derived from a progenitor cell.
 32. A method of treating a cancer in an individual, the method comprising: i) genetically modifying T lymphocytes obtained from the individual with an expression vector comprising nucleotide sequences encoding the heterodimeric, conditionally active CAR of claim 1, wherein the antigen-binding domain of the heterodimeric, conditionally active CAR is specific for an epitope on a cancer cell in the individual, and wherein said genetic modification is carried out ex vivo; ii) introducing the genetically modified T lymphocytes into the individual; and iii) administering to the individual an effective amount of a dimerizing agent, wherein the dimerizing agent induces dimerization of the heterodimeric, conditionally active CAR, wherein said dimerization provides for activation of the genetically modified T lymphocytes and killing of the cancer cell, thereby treating the cancer.
 33. The method of claim 32, wherein the dimerizing agent is a rapalog.
 34. A method of modulating the activity of a host cell, the method comprising contacting the host cell with a dimerizing agent and a second member of a specific binding pair, wherein the T lymphocyte is genetically modified to produce a heterodimeric, conditionally active CAR of claim 1, and wherein, in the presence of the dimerizing agent and the second member of a specific binding pair, the heterodimeric, conditionally active CAR dimerizes and modulates at least one activity of the host cell.
 35. The method of claim 34, wherein the activity is proliferation, cell survival, apoptosis, gene expression, or immune activation.
 36. The method of claim 34, wherein the second member of a specific binding pair is an antigen. 